Fix conditional for latest tag on GHCR (#889)

Author: abhinavsingh

.github/workflows/test-library.yml

@@ -744,7 +744,11 @@ jobs:
         }}'
         -t $CONTAINER_TAG .
     - name: Tag latest on GHCR
-      if: github.ref == 'ref/head/develop'
+      if: >-
+        github.event_name == 'push' &&
+        github.ref == format(
+          'refs/heads/{0}', github.event.repository.default_branch
+        )
       run: >-
         REGISTRY_URL="ghcr.io/abhinavsingh/proxy.py";
         LATEST_TAG=$REGISTRY_URL:latest;