fix: Target correct branch within CLA workflow

[alessfg]

Proposed changes

The CLA implementation in #970 was targeting the wrong branch in the signature data store. This PR fixes the issue.

Checklist

Before creating a PR, run through this checklist and mark each as complete:

• I have read the contributing guidelines
• I have signed the F5 Contributor License Agreement (CLA)
• I have run ./update.sh and ensured all entrypoint/Dockerfile template changes have been applied to the relevant image entrypoint scripts & Dockerfiles
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• I have updated any relevant documentation (README.md and/or modules/README.md)

[github-actions]

✅ All required contributors have signed the F5 CLA for this PR. Thank you!
_{Posted by the CLA Assistant Lite bot.}