Remove unnecessary Java steps

.github/workflows/docker.yml

@@ -8,10 +8,6 @@ jobs:
   docker:
     runs-on: ubuntu-latest
     env:
-      # Give Maven 1GB of memory to work with
-      # Suppress all Maven "downloading" messages in logs (see https://stackoverflow.com/a/35653426)
-      # This also slightly speeds builds, as there is less logging
-      MAVEN_OPTS: "-Xmx1024M -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=warn"
       # Define tags to use for Docker images based on Git tags/branches
       # For a new branch commit, tag Docker image with that branch name
       # Except for 'main' branch, where we use the literal 'dspace-7_x' tag (see below).
@@ -26,13 +22,6 @@ jobs:
       - name: Checkout codebase
         uses: actions/checkout@v2
 
-      # https://github.com/actions/setup-java
-      - name: Install JDK 11
-        uses: actions/setup-java@v2
-        with:
-          java-version: 11
-          distribution: 'temurin'
-
       - name: Setup Docker Buildx
         uses: docker/setup-buildx-action@v1