Fix incorrect completion() signature for Databricks provider

[terrytangyuan]

This fixes the following protocol compliance check:

Method completion incompatible proto: {'logprobs', 'model', 'sampling_params', 'stream', 'content'} vs. obj: {'request'}
...
    check_protocol_compliance(impl, protocols[provider_spec.api])
  File "/app/llama-stack-source/llama_stack/distribution/resolver.py", line 321, in check_protocol_compliance
    raise ValueError(
ValueError: Provider `remote::databricks (Api.inference)` does not implement the following methods:
[('completion', 'signature_mismatch')]

Also fixed some issues identified by pre-commit checks.

[ashwinb]

thank you!!!

[terrytangyuan]

@ashwinb You might want to get #237 in as well to prevent this from happening going forward.