Use only CSS to truncate commit message in blame

What does this MR do?

Changes to use pure CSS to truncate commit message in blame.

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

While I chose 450px as max-width to took care fluid layout including author's intention of !6218 (merged), what do you think is the best for td.blame-commit in files.scss?

While I finally chose 400px as max-width to took care fluid layout including author's intention of !6218 (merged), what do you think is the best for td.blame-commit in files.scss?

Why was this MR needed?

While this bug has existed since 2012 (34cea1cb, 9cd8f7b0), we should fix it to keep UX better.

Screenshots (if relevant)

before	after

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [n/a] Documentation created/updated
• [n/a] API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #35163 (closed)