add setup java to format task

.forgejo/workflows/format.yaml

@@ -9,6 +9,11 @@ jobs:
     runs-on: docker
     steps:
       - uses: actions/checkout@v4
+      - uses: actions/setup-java@v4
+        with:
+          java-version: '21'
+          distribution: 'temurin'
+          cache: 'gradle'
       - uses: axel-op/googlejavaformat-action@v3
         with:
           args: "--replace"