docs: add changelog entry for content_category re-deploy fix (#4110)

[zackverham]

Missing changelog entry for content_category fix

[posit-connect-projects]

Claude finished @zackverham's task in 34s —— View job

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Code Review Complete

• Gather context and read changed files
• Review changelog entry format and content
• Provide review feedback

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Review: Approved ✅

This changelog entry looks good:

• Format: Follows Keep a Changelog conventions correctly
• Placement: Properly added under ### Fixed in [Unreleased] section
• Issue reference: References issue Static HTML re-deploy fails with 403 error code 110 "cannot change categorization of content" #4110 as required by repo guidelines
• User perspective: Clearly describes the problem from the user's viewpoint (re-deploying static HTML content failing with Connect error 110)
• Context: Provides helpful examples (e.g., Quarto sites) and mentions the root cause (content_category)

The entry accurately documents the fix from PR #4112. No changes needed.