chore: explicitly state we should use java 8 in github action

Author: ldetmer

.github/workflows/prepare-release.yml

@@ -18,7 +18,11 @@ jobs:
     steps:
       - name: Check out code
         uses: actions/checkout@v4
-
+      - name: Set up JDK 8
+        uses: actions/setup-java@v3
+        with:
+          java-version: '8'
+          distribution: 'temurin' # or 'adopt'
       - name: Check input
         run: |
           echo '* input project: "${{ github.event.inputs.project }}"'