generator: allow analyzer v5, require at least 2.4.0 (Dart 2.14) (#25)

Author: greenrobot-team

generator/pubspec.yaml

@@ -9,7 +9,7 @@ environment:
 
 dependencies:
   objectbox: 1.6.2
-  analyzer: '>=1.1.0 <5.0.0'
+  analyzer: '>=2.4.0 <6.0.0'
   build: ^2.0.0
   collection: ^1.15.0
   dart_style: ^2.0.0