chore: Override PHP default changelog sections

[devin-ai-integration]

Requirements

• I have added test coverage for new or changed functionality — N/A, config-only change
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions — N/A, config-only change

Related issues

Applies the same fix from php-server-sdk#233 to this repository.

Describe the solution you've provided

The php release type in release-please includes a default changelog section configuration that causes chore commits to appear in release changelogs. This breaks the norm with other LaunchDarkly SDKs, which typically exclude chores from releases.

This PR explicitly sets changelog-sections to only include feat and fix commit types, so that chore changes no longer trigger or appear in releases.

Describe alternatives you've considered

None — this matches the established pattern already applied to php-server-sdk.

Additional context

• Link to Devin run
• Requested by: @keelerm84

[devin-ai-integration]

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