Use published source_gen_test.

Author: davidmorgan

json_serializable/pubspec.yaml

@@ -38,7 +38,7 @@ dev_dependencies:
   build_verify: ^3.0.0
   collection: ^1.17.0
   logging: ^1.0.0
-  source_gen_test: ^1.0.6
+  source_gen_test: ^1.2.0-dev
   test: ^1.24.4
   test_descriptor: ^2.0.0
   test_process: ^2.0.0
@@ -51,7 +51,3 @@ dependency_overrides:
       url: https://github.com/dart-lang/source_gen
       path: source_gen
       ref: 6c9702e7152e61b16c8adec3f3011bda738b0e29
-  source_gen_test:
-    git:
-      url: https://github.com/kevmoo/source_gen_test
-      ref: 9036882e5d69620fa387c14e880ebbe19ed99fee