chore: Override PHP default changelog sections

[devin-ai-integration]

Summary

Adds explicit changelog-sections configuration to release-please-config.json, limiting changelog entries to only feat (Features) and fix (Bug Fixes) types. This prevents chore commits from triggering releases and appearing in changelogs.

This is a port of the fix from php-server-sdk#233. The PHP release type in release-please is one of the few types that includes chore commits in changelogs by default, which is inconsistent with other LaunchDarkly SDKs.

Review & Testing Checklist for Human

• Verify the changelog-sections values match what was merged in php-server-sdk#233
• Confirm that only feat and fix are the desired section types (no perf, refactor, etc.)

Notes

Requested by: @keelerm84
Link to Devin run

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring