Update workflow to 17

Author: DevUt

.github/workflows/flutter-ci.yml

@@ -20,7 +20,7 @@ jobs:
       - uses: actions/checkout@v1
       - uses: actions/setup-java@v1
         with:
-          java-version: '12.x'
+          java-version: '17'
 
       - name: Decode Keystore
         env: