Fix Fireworks Callbacks (#12003)

I may be missing something but it seems like we inappropriately overrode
the 'stream()' method, losing callbacks in the process. I don't think
(?) it gave us anything in this case to customize it here?

See new trace:

https://smith.langchain.com/public/fbb82825-3a16-446b-8207-35622358db3b/r

and confirmed it streams.

Also fixes the stopwords issues from #12000

libs/langchain/langchain/llms/fireworks.py

@@ -6,9 +6,7 @@ from langchain.callbacks.manager import (
 )
 from langchain.llms.base import LLM, create_base_retry_decorator
 from langchain.pydantic_v1 import Field, root_validator
-from langchain.schema.language_model import LanguageModelInput
 from langchain.schema.output import GenerationChunk
-from langchain.schema.runnable.config import RunnableConfig
 from langchain.utils.env import get_from_dict_or_env
 
 
@@ -140,42 +138,6 @@ class Fireworks(LLM):
             if run_manager:
                 await run_manager.on_llm_new_token(chunk.text, chunk=chunk)
 
-    def stream(
-        self,
-        input: LanguageModelInput,
-        config: Optional[RunnableConfig] = None,
-        *,
-        stop: Optional[List[str]] = None,
-        **kwargs: Any,
-    ) -> Iterator[str]:
-        prompt = self._convert_input(input).to_string()
-        generation: Optional[GenerationChunk] = None
-        for chunk in self._stream(prompt):
-            yield chunk.text
-            if generation is None:
-                generation = chunk
-            else:
-                generation += chunk
-        assert generation is not None
-
-    async def astream(
-        self,
-        input: LanguageModelInput,
-        config: Optional[RunnableConfig] = None,
-        *,
-        stop: Optional[List[str]] = None,
-        **kwargs: Any,
-    ) -> AsyncIterator[str]:
-        prompt = self._convert_input(input).to_string()
-        generation: Optional[GenerationChunk] = None
-        async for chunk in self._astream(prompt):
-            yield chunk.text
-            if generation is None:
-                generation = chunk
-            else:
-                generation += chunk
-        assert generation is not None
-
 
 def completion_with_retry(
     llm: Fireworks,