Add pub cache clean to force cache refresh in CI

Author: DataSab

.github/workflows/flutter-web.yml

@@ -17,6 +17,9 @@ jobs:
         flutter-version: '3.24.0'
         channel: 'stable'
 
+    - name: Clear pub cache
+      run: flutter pub cache clean
+      
     - name: Install dependencies
       run: flutter pub get