chore: update flutter toolchain version to flutter 3.0

.github/workflows/ci.yaml

@@ -34,6 +34,7 @@ jobs:
         with:
           channel: 'stable'
           cache: true
+          flutter-version: '3.0.0'
 
       - name: Cache Cargo
         uses: actions/cache@v2

.github/workflows/release.yml

@@ -50,6 +50,7 @@ jobs:
         uses: subosito/flutter-action@v2
         with:
           channel: 'stable'
+          flutter-version: '3.0.0'
 
       - name: Pre build
         working-directory: frontend
@@ -98,6 +99,7 @@ jobs:
         uses: subosito/flutter-action@v2
         with:
           channel: 'stable'
+          flutter-version: '3.0.0'
 
       - name: Pre build
         working-directory: frontend