fix: target correct base branch for docker-versions PR (#1848)

The workflow was creating PRs against the default branch (main) instead of
the branch where it was running. When running on weekly, this caused PRs
trying to merge the entire weekly history into main.

Now extracts the current branch from GITHUB_REF and uses it as the base
branch for the PR, ensuring docker-versions updates stay on the same branch.

Author: gounthar

.github/workflows/github-docker-registry-push.yml

@@ -57,7 +57,9 @@ jobs:
           else
             git commit -m "Update Docker versions"
             git push origin docker-versions-update
-            echo 'y' | gh pr create --fill
+            # Create PR targeting the same branch where this workflow is running
+            BASE_BRANCH="${GITHUB_REF#refs/heads/}"
+            echo 'y' | gh pr create --fill --base "$BASE_BRANCH"
           fi
 
       - name: Check for Dockerfile and context changes