Update to labeler@v4

[sabiurr]

What does this PR do?

Update to labeler@v4. The labeler github action is failing https://github.com/DataDog/datadog-serverless-functions/actions/runs/5807388470/job/16560137170?pr=686

Motivation

The labeler github action is failing https://github.com/DataDog/datadog-serverless-functions/actions/runs/5807388470/job/16560137170?pr=686

Testing Guidelines

Additional Notes

Types of changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
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