(maint) Update labeller.yml to pull_request

[pmcmaw]

Summary

Provide a detailed description of all the changes present in this pull request.

Additional Context

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• [ ] Root cause and the steps to reproduce. (If applicable)
• [ ] Thought process behind the implementation.

Related Issues (if any)

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Checklist

• [ ] 🟢 Spec tests.
• [ ] 🟢 Acceptance tests.
• [ ] Manually verified.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.10%. Comparing base (fa44143) to head (d60f85d).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #320 +/- ## ======================================= Coverage 92.10% 92.10% ======================================= Files 6 6 Lines 722 722 ======================================= Hits 665 665 Misses 57 57 ```

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