Update dargon2_flutter_tests.yml

Author: tmthecoder

.github/workflows/dargon2_flutter_tests.yml

@@ -16,6 +16,10 @@ jobs:
         uses: actions/checkout@v2
         with:
           submodules: recursive
+      - name: Setup Java
+        uses: actions/setup-java@v2
+        with:
+         java-version: '17'
       - name: Gradle cache
         uses: actions/cache@v2
         with: