Fix: Skip deletion of main branch in release pipeline

Add conditional check to prevent attempting to delete the main branch when promoting, as GitHub does not allow deletion of the default branch remotely. This resolves the workflow failure in the 'Promote and delete source' step.

Co-authored-by: jmiller-moko <230051081+jmiller-moko@users.noreply.github.com>

.github/workflows/release_pipeline.yml

@@ -314,7 +314,11 @@ jobs:
 
           git checkout -B "${DST}" "origin/${SRC}"
           git push origin "${DST}"
-          git push origin --delete "${SRC}"
+
+          # Skip deletion of main branch as GitHub does not allow deleting the default branch
+          if [ "${SRC}" != "main" ]; then
+            git push origin --delete "${SRC}"
+          fi
 
           {
             echo "### Promotion report"