patch: remove usage of llm, chat model __call__ (#20788)

- `llm(prompt)` -> `llm.invoke(prompt)`
- `llm(prompt=prompt` -> `llm.invoke(prompt)` (same with `messages=`)
- `llm(prompt, callbacks=callbacks)` -> `llm.invoke(prompt,
config={"callbacks": callbacks})`
- `llm(prompt, **kwargs)` -> `llm.invoke(prompt, **kwargs)`

libs/community/tests/integration_tests/llms/test_openlm.py

@@ -4,5 +4,5 @@ from langchain_community.llms.openlm import OpenLM
 def test_openlm_call() -> None:
     """Test valid call to openlm."""
     llm = OpenLM(model_name="dolly-v2-7b", max_tokens=10)
-    output = llm(prompt="Say foo:")
+    output = llm.invoke("Say foo:")
     assert isinstance(output, str)