Update to flutter 3.35

Author: sheldonrobinson

src/serious_python/example/flask_example/pubspec.yaml

@@ -19,8 +19,8 @@ publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 version: 1.0.0+1
 
 environment:
-  sdk: ">=3.0.3 <4.0.0"
-  flutter: ">=3.7.0"
+  sdk: '>=3.7.0 < 4.0.0'
+  flutter: '>=3.27.0'
 
 # Dependencies specify other packages that your package needs in order to work.
 # To automatically upgrade your package dependencies to the latest versions