fix(ci): update test-beta matrix

Author: socheatsok78

.github/workflows/dart.yml

@@ -37,7 +37,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        version: [3.0.1, 3.1.0-9.0.pre]
+        version: [3.1.0, 3.1.0-9.0.pre]
     steps:
       - uses: actions/checkout@v2
       - uses: ./