Follow-up to #14215

Description

PR #14215 made --comments and --json mutually exclusive for discussion views, but four discussion acceptance-test commands still passed both flags. Remove --comments from those JSON assertions because requesting the comments JSON field already fetches the full comment data.

How did you test this change?

➜  williammartin-psychic-doodle git:(williammartin-psychic-doodle) GH_ACCEPTANCE_HOST=github.com \
GH_ACCEPTANCE_ORG=gh-acceptance-testing \
GH_ACCEPTANCE_TOKEN="$(gh auth token --hostname github.com)" \
go test -tags=acceptance ./acceptance -run '^TestDiscussions$'
ok      github.com/cli/cli/v2/acceptance        56.809s

Key points

The standalone --comments acceptance case remains unchanged so human-readable comment output is still covered.

Notes for reviewers

Start with acceptance/testdata/discussion/discussion-comment.txtar. PR #14215 introduced the mutual exclusion that exposed these stale commands.

Authorship and follow-up

Who wrote this:

• A human wrote it.
• An agent wrote it under close human direction.
• An agent wrote it independently, and no human has guided the implementation beyond the initial prompt.

Who answers review comments:

• @williammartin will read and reply directly.
• An agent will draft replies and @username will read them before they are posted.
• Nobody has explicitly committed to replying.