Amend DOCKER_PUSH conditional (#1245)

Author: charlesbluca

Diff for: .github/workflows/docker.yml

@@ -25,7 +25,7 @@ jobs:
     name: Push Docker image to Docker Hub
     runs-on: ubuntu-latest
     env:
-      DOCKER_PUSH: ${{ contains(['push', 'release'], github.event_name) && github.repository == 'dask-contrib/dask-sql' }}
+      DOCKER_PUSH: ${{ contains(fromJSON('["push", "release"]'), github.event_name) && github.repository == 'dask-contrib/dask-sql' }}
     strategy:
       fail-fast: false
       matrix: