Locking dart version in action workflows

Author: Mikael Wills

.github/workflows/dart.yml

@@ -22,7 +22,7 @@ jobs:
           java-version: '12.x'
       - uses: subosito/flutter-action@v1
         with:
-          channel: 'stable'
+          flutter-version: '3.27.1'
       - name: Install project dependencies
         run: flutter pub get
       - name: Dart Format Check

.github/workflows/pushMaster.yaml

@@ -14,7 +14,7 @@ jobs:
       - name: Install Flutter
         uses: subosito/flutter-action@v2
         with:
-          channel: "stable"
+          flutter-version: "3.27.1"
       - name: Install project dependencies
         run: flutter pub get
       - name: Dart Format Check