T8100: Add circinus branch to labeler configuration

[kumvijaya]

Change Summary

Added the circinus branch to the GitHub Actions labeler configuration to ensure PRs targeting the circinus branch are automatically labeled with the appropriate branch name label.

Changes

• Added circinus label configuration to .github/labeler.yml with base-branch matching rule

Related Issues

• Fixes issue where circinus PRs were not receiving the branch name label

PRs targeting the circinus branch should now automatically receive the circinus label.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Other (please describe):

Related Task(s)

https://vyos.dev/T8100

Related PR(s)

Proposed changes

How to test

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly