[Schema Inaccuracy] Fix media types in rest/gists/comments.md

[cmwilson21]

Transferring an OS PR over. - github/docs#22245

The media types seem to be wrong on the page https://docs.github.com/en/rest/gists/comments

To test the current ones, which seem to have no effect:

$ curl --silent -H "Accept: application/vnd.github.3.base64+json" https://api.github.com/gists/9257657/comments/1221189 | grep body 
  "body": "Thanks, Octocat!\n"

To test the new ones, which have an effect:

$ curl --silent -H "Accept: application/vnd.github.3.full+json" https://api.github.com/gists/9257657/comments/1221189 | grep body 
  "body_html": "<p dir=\"auto\">Thanks, Octocat!</p>",
  "body_text": "Thanks, Octocat!",
  "body": "Thanks, Octocat!\n"

Check off the following:

• I have reviewed my changes in staging (look for the "Automatically generated comment" and click the links in the "Preview" column to view your latest changes).
• For content changes, I have completed the self-review checklist.

[maflcko]

I don't think this is an issue with the schema, or requires changing the schema. Please see above steps to reproduce to confirm the current schema is correct. Also, the current documentation at https://docs.github.com/en/rest/overview/media-types?apiVersion=2022-11-28#comment-body-properties mentions the correct media types.

The only issue is the media types mentioned on the gist comments page itself, which is fixed by github/docs#22245

[maflcko]

For context, the docs were initially added in github/docs@2ade7d8#diff-c3115422ae00cbd3b9a9d865e26c4412c93a1c368962e1938027d170c061ffaf