fix typo in shadow policy

fmoe/fastermoe/shadow_policy.py

@@ -69,5 +69,5 @@ def get_shadow_policy(d_model=None):
     if d_model is not None and 'FMOE_FASTER_GLBPLC_DMODEL' not in os.environ:
         os.environ['FMOE_FASTER_GLBPLC_DMODEL'] = str(d_model)
     if not switch_from_env('FMOE_FASTER_SHADOW_ENABLE'):
-        return no_policy
+        return no_shadow_policy
     return global_policy