docs: fix SDL best practices formatting

[tharune]

Summary

• close bold markers in the SDL best-practices pitfall headings
• remove stray Markdown bold markers from YAML comments that are meant to render literally

Verification

• inspected the affected Markdown around the Common Pitfalls section
• ran git diff --check

[tharune]

Closing as duplicate after audit. These SDL best-practices formatting fixes are included in the broader open PR #1174.