Update testingbranch.yml

Author: ryma2fhir

.github/workflows/testingbranch.yml

@@ -20,6 +20,11 @@ jobs:
       - uses: actions/checkout@v4
         with:
           submodules: true
+      
+      - uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: '21'
 
       - name: Check out validation-service-fhir-r4
         uses: actions/checkout@master