chore(ci): Remove flutter-version specification from CI configuration

- Eliminated the flutter-version line in the CI workflow to streamline the setup process, relying on the channel specification instead.

Author: koniz-dev

.github/workflows/ci.yml

@@ -38,7 +38,6 @@ jobs:
       - name: Setup Flutter
         uses: subosito/flutter-action@v2
         with:
-          flutter-version: 'stable'
           channel: 'stable'
           cache: true