chore: Override PHP default changelog sections

[devin-ai-integration]

Summary

Adds explicit changelog-sections configuration to release-please-config.json to only include feat and fix commits in changelogs. The PHP release type in release-please uniquely defaults to including chore commits in releases, which is inconsistent with our other SDKs. This was already fixed in php-server-sdk#233 and this PR applies the same fix here.

Review & Testing Checklist for Human

• Verify the changelog-sections entries match the format used in php-server-sdk#233
• Confirm release-please-config.json is still valid JSON after the change

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