Try fixing 'if' on task build

Author: ChrisPenner

.github/workflows/ci.yaml

@@ -195,7 +195,7 @@ jobs:
 
   # Separate jobs for the docker builds because they requires elevated github token permissions.
   share-task-runner-docker-build:
-    if: env.is_task_build
+    if: ${{ github.event_name == 'push' && startsWith(github.ref, 'refs/heads/task-') }}
     env:
       container_registry: ghcr.io
       docker_image_name: share-task-runner