Rename test case variables, Remove redundant string prefix assertions
in TestAuthErrWithoutBody and TestFatalWithoutBody where the error type is already validated.

In a prior commit in this PR we removed a pair of assertions from
the TestAuthErrWithoutBody() and TestFatalWithoutBody() Go test
functions in our "lfsapi/response_test.go" source file, with the
understanding that these assertions were redundant.

However, these assertions explicitly verify that the NewAuthError()
and NewFatalError() functions from our "errors" package wrap their
error parameters with the strings "Authentication required" and
"Fatal error", respectively.

As well, the assertions in the TestAuthErrWithoutBody() and
TestFatalWithoutBody() functions also checked some of the error
messages defined by the defaultError() function in our "lfshttp"
package, specifically the "Authorization error" and "Server error"
messages for the HTTP status codes 401 and 500, respectively.

We therefore restore these two assertions, as they have some value
in checking that our error messages for specific HTTP conditions
match our expectations.

In prior commits in this PR we introduced several new Go test
functions to our "lfsapi" and "tq" packages, including the
TestRateLimitedWithBody() and TestRateLimitedWithoutBody() functions
in the former package and the TestCanRetryObjectLater() function in
the latter package.  These functions each define and verify multiple
test cases, using anonymous structures with a number of fields,
not all of which are used in every test case.

We can simplify the definitions of these test cases slightly by
relying on Go to initialize certain string and Boolean fields with
the appropriate default values, namely the empty string and the
"false" value, respectively.

In prior commits in this PR we introduced several new Go test
functions to our "lfsapi" and "tq" packages, including the
TestRateLimitedWithBody() and TestRateLimitedWithoutBody() functions
in the former package and the TestCanRetryObjectLater() function in
the latter package.  These functions each define and verify multiple
test cases, using anonymous structures with a number of fields,
some of which specify the expected state after the condition
defined by the test case is simulated.

In a previous commit, we renamed these types of fields in the
test case structures of the TestRateLimitedWithBody() and
TestRateLimitedWithoutBody() functions so they begin with the
prefix "expected" rather than "want".  We made this change because
we already have a number of other test case structures which
follow this naming scheme, such as the "dirWalkerWalkTestCase"
structure in our "tools" package.

We now make the same change for the test case structure in our
new TestCanRetryObjectLater() function, for the same reason.

In a prior commit in this PR we added two new shell integration
tests named "batch storage HTTP upload abandons when Retry-After
exceeds maxRetryTime" and "batch storage HTTP download abandons
when Retry-After exceeds maxRetryTime" to our
"t/t-batch-storage-retries-ratelimit.sh" shell script.

The intent of these tests is to verify that when the Git LFS client
makes a request to upload or download an individual object and
receives a 429 status code response with a Retry-After header, if
the value of that header is greater than that specified by our new
"lfs.transfer.maxRetryTime" configuration option, then the client
will report an error and not retry the object transfer request.

We can expand these tests slightly by adding a call to our
refute_server_object() assertion function at the end of the test
which expects an object upload to fail, and by adding a call to
our refute_local_object() assertion function at the end of the
test which expects an object download to fail.

As well, we indent the lines in the latter test which appear between
"pushd" and "popd" shell built-in commands, in order to match the
formatting of our other shell tests which use these commands.

We also add comments to explain that the contents of the objects
created by the tests are significant, as they signal to the test
server utility that it should return 429 status code responses
with Retry-After headers to the initial object transfer requests
it receives for an object.

Finally, we rename the tests slightly and make a few other revisions
to bring their format into alignment with our current idiom for new
shell integration tests.

In prior commits in this PR we implemented a new configuration
option for the Git LFS client named "lfs.transfer.maxRetryTime",
and then added documentation of the new option to our
git-lfs-config(5) manual page.

We now adjust that documentation slightly to correct one typo,
and also take the opportunity to simplify the description of
the "lfs.transfer.maxRetryTime" option's default value by using
a numeral value of 300.

Although we describe several of our other similar options' default
values using words (e.g., "eight" and "ten"), these are single words
rather than multiple words, and in any case we should probably revise
them to numerals in a future PR in order to align them with the
prevailing style of both our documentation and that of the Git project.

As well, we format the new option's name using the camel-case style
found in the Git project's own documentation, and which we are
slowly trying to adopt in our own documentation.