[Python Misc] Add CSM package to verify_python_release (#36963)

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Closes #36963

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/36963 from XuanWang-Amos:add_csm_to_verify_python_release 3e64130771
PiperOrigin-RevId: 644470995

tools/release/verify_python_release.py

@@ -45,6 +45,7 @@ _DEFAULT_PACKAGES = [
     "grpcio-admin",
     "grpcio-csds",
     "grpcio-observability",
+    "grpcio-csm-observability",
     "xds-protos",
 ]