The API reference code block built every class member signature with a
return type, so constructors were rendered as invalid TypeScript:

  class ActivationStart {
    constructor(snapshot: ActivatedRouteSnapshot): ActivationStart;
  }

Constructors are extracted as regular method entries whose return type is
the class itself, so `getMethodCodeLine` now omits the return type when
the member is a constructor, for both the single signature and the
overloaded cases:

  class ActivationStart {
    constructor(snapshot: ActivatedRouteSnapshot);
  }