fix: mirror_barretenberg_repository.yml

[ludamad]

We had a master/main difference so copying over the docs mirror action as-is didn't work out.

Checklist:

• I have reviewed my diff in github, line by line.
• Every change is related to the PR description.
• I have linked this pull request to the issue(s) that it resolves.
• There are no unexpected formatting changes, superfluous debug logs, or commented-out code.
• The branch has been merged or rebased against the head of its merge target.
• I'm happy for the PR to be merged at the reviewer's next convenience.

[netlify]

✅ Deploy Preview for preeminent-bienenstitch-606ad0 canceled.

Name	Link
🔨 Latest commit	d8efdbe
🔍 Latest deploy log	https://app.netlify.com/sites/preeminent-bienenstitch-606ad0/deploys/64c12f859f773700080e3d33

[Maddiaa0]

stupendous