Resolve "Fix the following style-lint errors and warnings for `app/assets/stylesheets/pages/commits.scss`"

What does this MR do?

This MR fixes the stylelint errors for commits.scss.

Some classes were either not used (.notes_count, .commited_ago) or in the wrong format (.generic_commit_status -> .generic-commit-status).

Other classes were unnecessary and were replaced by utility classes.

Below are some screenshots of before and after, but the results look the same because no styling was changed just how it was implemented.

There is an EE backport where there was also a wrongly formatted class (.project_namespace): https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/11902

	Commits	Commit Description	Commit Component
before
after

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #59898 (closed)