ci: Fix release workflows (#900)

Author: mtrezza

.github/workflows/release-automated.yml

@@ -23,6 +23,8 @@ jobs:
       - name: Setup dart
         # if: env.package == 'dart'
         uses: dart-lang/setup-dart@v1
+        with:
+          sdk: '3.0.0'
       - name: Setup flutter
         if: env.package == 'flutter'
         uses: subosito/flutter-action@v2

.github/workflows/release-manual.yml

@@ -26,6 +26,8 @@ jobs:
       - name: Setup dart
         # if: env.package == 'dart'
         uses: dart-lang/setup-dart@v1
+        with:
+          sdk: '3.0.0'
       - name: Setup flutter
         if: env.package == 'flutter'
         uses: subosito/flutter-action@v2