fix(deps): update dependency source_gen to v2 (#33)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

pubspec.yaml

@@ -10,7 +10,7 @@ dependencies:
   build: ^2.2.1
   path: ^1.8.0
   recase: ^4.0.0
-  source_gen: ^1.2.7
+  source_gen: ^2.0.0
   meta: ^1.10.0
   logger: ^1.1.0
   stacked_shared: ^1.3.0