[Python example] Fix version in generated code in example folder (#37665)

Fix: https://github.com/grpc/grpc/issues/37610
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examples/python/helloworld/helloworld_pb2_grpc.py

@@ -5,7 +5,7 @@ import warnings
 
 import helloworld_pb2 as helloworld__pb2
 
-GRPC_GENERATED_VERSION = '1.67.0.dev0'
+GRPC_GENERATED_VERSION = '1.66.0'
 GRPC_VERSION = grpc.__version__
 _version_not_supported = False