Switch to java flavour

.forgejo/workflows/build-and-test.yml

@@ -8,10 +8,8 @@ jobs:
  build:
   runs-on: docker
   container:
-   image: git.staropensource.de/staropensource/actions-docker:latest
+   image: git.staropensource.de/staropensource/actions-docker:java
   steps:
-   - name: Install latest OpenJDK release
-     run: pacman -S --noconfirm jdk-openjdk
    - name: Checkout
      uses: https://code.forgejo.org/actions/checkout@v4
    - name: Compile