community[patch]: callback before yield for google palm (#26882)

**Description:** Moves yield to after callback for `_stream` function
for the google palm model in the community package
**Issue:** #16913

libs/community/langchain_community/llms/google_palm.py

@@ -215,13 +215,13 @@ class GooglePalm(BaseLLM, BaseModel):
             **kwargs,
         ):
             chunk = GenerationChunk(text=stream_resp.text)
-            yield chunk
             if run_manager:
                 run_manager.on_llm_new_token(
                     stream_resp.text,
                     chunk=chunk,
                     verbose=self.verbose,
                 )
+            yield chunk
 
     @property
     def _llm_type(self) -> str: