fix: update build_test dependency version to >=2.0.0 <4.0.0 in pubspec files

Author: gibahjoe

openapi-generator/pubspec.yaml

@@ -22,7 +22,7 @@ dependencies:
 dev_dependencies:
   test: ^1.24.2
   mockito: ^5.4.4
-  build_test: '>=1.2.0 <3.0.0'
+  build_test: '>=2.0.0 <4.0.0'
   source_gen_test:
   test_process:
   build_runner:

openapi-generator/test/specs/dart_pubspec.test.yaml

@@ -17,5 +17,5 @@ dependencies:
 dev_dependencies:
   test: ^1.24.2
   build_runner: '>=1.0.0 <3.0.0'
-  build_test: '>=1.2.0 <3.0.0'
+  build_test: '>=2.0.0 <4.0.0'
   coverage: ^1.6.3

openapi-generator/test/specs/flutter_pubspec.test.yaml

@@ -19,5 +19,5 @@ dependencies:
 dev_dependencies:
   test: ^1.24.2
   build_runner: '>=1.0.0 <3.0.0'
-  build_test: '>=1.2.0 <3.0.0'
+  build_test: '>=2.0.0 <4.0.0'
   coverage: ^1.6.3