Generator: for Flutter, allow collection 1.18.0, require Dart 3.5

Require Dart 3.5 because Flutter SDK 3.24.0 is required to get high
enough meta version required by analyzer and pinned by Flutter SDK.

Author: greenrobot-team

generator/pubspec.yaml

@@ -6,13 +6,13 @@ homepage: https://objectbox.io
 version: 4.1.0
 
 environment:
-  sdk: '^3.4.0' # analyzer 6.5.0 requires macros >=0.1.0-main.0 requires >=3.4.0-256.0.dev
+  sdk: '^3.5.0' # analyzer 6.5.0 requires meta 1.14.0 requires Flutter SDK 3.24.0 requires 3.5.0
 
 dependencies:
   objectbox: 4.1.0
   analyzer: '>=6.5.0 <8.0.0' # dart_style 2.3.7 requires 6.5.0
   build: ^2.4.1
-  collection: ^1.19.1
+  collection: ^1.18.0 # Would require 1.19.1, but Flutter 3.24.0 has 1.18.0 pinned
   dart_style: '>=2.3.7 <4.0.0' # require 2.3.7 for languageVersion in DartFormatter constructor
   glob: ^2.1.3
   path: ^1.9.1