re-add java setup

Author: farrell-m

.github/workflows/push-branch.yml

@@ -65,6 +65,11 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
+      - name: Set up JDK 21
+        uses: actions/setup-java@v3
+        with:
+          java-version: '21'
+          distribution: 'temurin'
       - uses: snyk/actions/setup@0.4.0
       - name: Install snyk-delta
         run: |