Downgrade build_runner_core to <9.0.0

Signed-off-by: Gavin Zhao <git@gzgz.dev>

Author: GZGavinZhao

ngcompiler/pubspec.yaml

@@ -26,6 +26,7 @@ dependencies:
   path: ^1.9.1
   source_gen: ^1.5.0
   source_span: ^1.10.1
+  build_runner_core: <9.0.0
 
 dev_dependencies:
   build_test: ^2.2.2