Update actions/setup-java action to v2 (#195)

Co-authored-by: Renovate Bot <[email protected]>

Author: renovate[bot]

.github/workflows/dart.yml

@@ -16,7 +16,7 @@ jobs:
 #        os: [ubuntu-latest, windows-latest, macos-latest]
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-java@v1
+      - uses: actions/setup-java@v2
         with:
           java-version: '12.x'
       - uses: subosito/flutter-action@v1