fix: pubspec.yaml small fixes

packages/ada_chat_flutter/pubspec.yaml

@@ -3,7 +3,7 @@ description: Flutter implementation of Ada chat
 version: 1.0.0
 
 environment:
-  sdk: '>=3.0.0 <4.0.0'
+  sdk: '>=3.3.0 <4.0.0'
   flutter: ">=3.19.0"
 
 dependencies:
@@ -16,7 +16,7 @@ dev_dependencies:
   flutter_lints: ^4.0.0
   flutter_test:
     sdk: flutter
-  mocktail: ^1.0.3 # Used by MockWebViewDependencies() tests helper
+  mocktail: ^1.0.3
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec
@@ -28,9 +28,6 @@ flutter:
   # assets:
   #   - images/a_dot_burr.jpeg
   #   - images/a_dot_ham.jpeg
-  assets:
-    - assets/
-
   #
   # For details regarding assets in packages, see
   # https://flutter.dev/assets-and-images/#from-packages