similarity_score_threshold NotImplementedError

### System Info

Langchain 0.0.184
Python 3.9.2



### Who can help?

@hwchase17

### Information

- [ ] The official example notebooks/scripts
- [X] My own modified scripts

### Related Components

- [ ] LLMs/Chat Models
- [ ] Embedding Models
- [ ] Prompts / Prompt Templates / Prompt Selectors
- [ ] Output Parsers
- [ ] Document Loaders
- [X] Vector Stores / Retrievers
- [ ] Memory
- [ ] Agents / Agent Executors
- [ ] Tools / Toolkits
- [ ] Chains
- [ ] Callbacks/Tracing
- [ ] Async

### Reproduction

I'm using as_retriever in a RetrievalQA with Pinecone as the vector store. If i use search_type="similarity_score_threshold"  code below works. If I change this to `similarity_score_threshold` and set a `score_threshold`, then when I run the qa I get  NotImplementedError:

The code looks like this
```python
db = Pinecone.from_existing_index(index_name=os.environ.get('INDEX'), 
                                   namespace='SCA_H5', 
                                   embedding=OpenAIEmbeddings())

retriever=db.as_retriever(search_type="similarity_score_threshold", 
                          search_kwargs={"k":3, "score_threshold":0.5})

qa = RetrievalQA.from_chain_type(
                    llm=ChatOpenAI(temperature=0), # uses 'gpt-3.5-turbo' which is cheaper and better 
                    chain_type="stuff", 
                    retriever=retriever, 
                    return_source_documents=True)
```

The python Traceback is 

```python
NotImplementedError                       Traceback (most recent call last)
Cell In[4], line 1
----> 1 result = Simon("What does the legisltation cover", sources=True, content=False)

Cell In[3], line 26, in Simon(query, sources, content)
     21 def Simon(query, sources=True, content=False):
     23   instructions = '''You are an expert in Western Australia "Strata Titles Act" 
     24                     answering questions from a citizen. Only use information provided to you from the 
     25                     legislation below. If you do not know say "I do not know"'''
---> 26   result = qa({"query": f'{instructions} \n\n {query}'})
     27   process_llm_response(result, sources=sources, content=content)
     28   return (result)

File [~/Projects/Personal/SCAWA/.venv/lib/python3.9/site-packages/langchain/chains/base.py:140](https://file+.vscode-resource.vscode-cdn.net/home/kmcisaac/Projects/Personal/SCAWA/~/Projects/Personal/SCAWA/.venv/lib/python3.9/site-packages/langchain/chains/base.py:140), in Chain.__call__(self, inputs, return_only_outputs, callbacks)
    138 except (KeyboardInterrupt, Exception) as e:
    139     run_manager.on_chain_error(e)
--> 140     raise e
    141 run_manager.on_chain_end(outputs)
    142 return self.prep_outputs(inputs, outputs, return_only_outputs)

File [~/Projects/Personal/SCAWA/.venv/lib/python3.9/site-packages/langchain/chains/base.py:134](https://file+.vscode-resource.vscode-cdn.net/home/kmcisaac/Projects/Personal/SCAWA/~/Projects/Personal/SCAWA/.venv/lib/python3.9/site-packages/langchain/chains/base.py:134), in Chain.__call__(self, inputs, return_only_outputs, callbacks)
    128 run_manager = callback_manager.on_chain_start(
    129     {"name": self.__class__.__name__},
    130     inputs,
...
    165     0 is dissimilar, 1 is most similar.
    166     """
--> 167     raise NotImplementedError
```

### Expected behavior

The qa call does not fail.