Resolve "Issue note icons wrong color"

What does this MR do?

• remove overly specific btn styles for svgs (affected Note icons)
• remove .projects-list a style (affected project list CI icons
• add hover styles to ci-icons to override a:hover styles from bootstrap's scaffolding.scss

EE MR: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3565

Are there points in the code the reviewer needs to double check?

Also moved the .text-* styles to where the other color utils are. There may be a better place to put them

Screenshots (if relevant)

NB links in Project descriptions are now blue. I think this is better than current (they are plain text), but this prob needs a UX-ok

Does this MR meet the acceptance criteria?

• [ ] Changelog entry added, if necessary
• [ ] Documentation created/updated
• [ ] API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
• Conform by the merge request performance guides
• Conform by the style guides

What are the relevant issue numbers?

Closes #40459 (closed)