[7-2-stable] Fix changelogs lint for trailing whitespaces

[zzak]

Due to PR #51841 being created before rails/buildkite-config#105 was merged, lint job was still skipped and therefor we missed it.

Btw, if you need to test this locally you can run this from the root of your rails checkout:

$ bundle exec tools/railspect changelogs .

For example:

~/code/rails => bundle exec tools/railspect changelogs .
E.......E.E.E

Offenses:

actioncable/CHANGELOG.md:11 Trailing whitespace detected.

^^^^
activerecord/CHANGELOG.md:41 Trailing whitespace detected.
*   Add `ENV["SKIP_TEST_DATABASE_TRUNCATE"]` flag to speed up multi-process test runs on large DBs when all tests run within default transaction.
                                                                                                                                                 ^
activerecord/CHANGELOG.md:293 Trailing whitespace detected.

^^^^
activesupport/CHANGELOG.md:107 Trailing whitespace detected.

^^^^
railties/CHANGELOG.md:3 Trailing whitespace detected.

^^^^
railties/CHANGELOG.md:253 Trailing whitespace detected.

^^^^
13 changelogs inspected, 6 offenses detected

[zzak]

rubocop job fails due to #51857