chore: fix ci mpl head gha

Author: josecorella

.github/workflows/mpl-head.yml

@@ -17,7 +17,7 @@ jobs:
     if: github.event_name != 'schedule' || github.repository_owner == 'aws'
     uses: ./.github/workflows/mpl_head_version.yml
     with:
-      mpl-head: true
+      mpl-head: main
   mpl-head-ci-format:
     needs: getVersion
     if: github.event_name != 'schedule' || github.repository_owner == 'aws'