Remove docker layer caching

Docker images saved by hash, i.e. kind cluster image, don't work with
satackey docker layer caching, causing build to fail.
See satackey/action-docker-layer-caching#140

Remove the broken plugin from use.

.github/workflows/ci.yml

@@ -8,7 +8,6 @@ jobs:
   build-and-publish:
     runs-on: ubuntu-latest
     steps:
-      - uses: satackey/[email protected]
       - name: Checkout the repository
         uses: actions/checkout@v2
       - name: Setup Java