Fix Groq invalid self.config reference (#719)

# What does this PR do?

Contributes towards: #432

RE: #609

I missed this one while refactoring. Fixes:

```python
Traceback (most recent call last):
  File "/Users/aidand/dev/llama-stack/llama_stack/distribution/server/server.py", line 191, in endpoint
    return await maybe_await(value)
  File "/Users/aidand/dev/llama-stack/llama_stack/distribution/server/server.py", line 155, in maybe_await
    return await value
  File "/Users/aidand/dev/llama-stack/llama_stack/providers/utils/telemetry/trace_protocol.py", line 101, in async_wrapper
    result = await method(self, *args, **kwargs)
  File "/Users/aidand/dev/llama-stack/llama_stack/distribution/routers/routers.py", line 156, in chat_completion
    return await provider.chat_completion(**params)
  File "/Users/aidand/dev/llama-stack/llama_stack/providers/utils/telemetry/trace_protocol.py", line 101, in async_wrapper
    result = await method(self, *args, **kwargs)
  File "/Users/aidand/dev/llama-stack/llama_stack/providers/remote/inference/groq/groq.py", line 127, in chat_completion
    response = self._get_client().chat.completions.create(**request)
  File "/Users/aidand/dev/llama-stack/llama_stack/providers/remote/inference/groq/groq.py", line 143, in _get_client
    return Groq(api_key=self.config.api_key)
AttributeError: 'GroqInferenceAdapter' object has no attribute 'config'. Did you mean: '_config'?
```


## Test Plan

Environment:

```shell
export GROQ_API_KEY=<api-key>

# build.yaml and run.yaml files
wget https://raw.githubusercontent.com/aidando73/llama-stack/9165502582cd7cb178bc1dcf89955b45768ab6c1/build.yaml
wget https://raw.githubusercontent.com/aidando73/llama-stack/9165502582cd7cb178bc1dcf89955b45768ab6c1/run.yaml

# Create environment if not already
conda create --prefix ./envs python=3.10
conda activate ./envs

# Build
pip install -e . && llama stack build --config ./build.yaml --image-type conda

# Activate built environment
conda activate llamastack-groq
```
<details>
<summary>Manual</summary>

```bash
llama stack run ./run.yaml --port 5001
```

Via this Jupyter notebook:
https://github.com/aidando73/llama-stack/blob/9165502582cd7cb178bc1dcf89955b45768ab6c1/hello.ipynb
</details>


## Sources

Please link relevant resources if necessary.


## Before submitting

- [ ] This PR fixes a typo or improves the docs (you can dismiss the
other checks if that's the case).
- [x] Ran pre-commit to handle lint / formatting issues.
- [x] Read the [contributor
guideline](https://github.com/meta-llama/llama-stack/blob/main/CONTRIBUTING.md),
      Pull Request section?
- [x] Updated relevant documentation.
- [ ] Wrote necessary unit or integration tests.

llama_stack/providers/remote/inference/groq/groq.py

@@ -140,7 +140,7 @@ async def embeddings(
 
     def _get_client(self) -> Groq:
         if self._config.api_key is not None:
-            return Groq(api_key=self.config.api_key)
+            return Groq(api_key=self._config.api_key)
         else:
             provider_data = self.get_request_provider_data()
             if provider_data is None or not provider_data.groq_api_key: