Merge branch 'issues-list-class-migration' into 'master'

Issues list: Migrate classes to design tokens

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/172519



Merged-by: Tristan Read <tread@gitlab.com>
Approved-by: Annabel Dunstone Gray <annabel.dunstone@gmail.com>
Approved-by: Tristan Read <tread@gitlab.com>
Co-authored-by: Sascha Eggenberger <seggenberger@gitlab.com>