Reduce number of issues found by Rari in content

[caugner]

Since mdn/rari#488 we know how many issues there are across all content repos:

• 2026-01-27: 55,922 issues in 12,560 of 63,806 files
• 2026-04-09: 30,451 issues in 9,021 of 65,178 files

This issue tracks progress towards reducing that number significantly.