Sentence case access tokens

What does this MR do and why?

• Sentence case instances of access tokens:
  • Personal access tokens
  • Group access tokens
  • Project access tokens
• Update docs

➡ Note: There will be a follow-up MR to update the rest of the instances in the docs

Screenshots or screen recordings

Example:

Before	After

How to set up and validate locally

Links

• Related to ✂️ UX Paper Cuts 17.3 → Dark mode - Design Support (#452231 - closed)
• Related to Track cleaning up over-capitalized "personal ac... (#473285)