Merge pull request #107 from flutter-webrtc/renovate/actions-checkout-2.x

Update actions/checkout action to v2

Author: cloudwebrtc

.github/workflows/flutter.yml

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