Update s3.py

[llama-shepard]

What does this PR do?

This PR is a fix for lorax.errors.GenerationError: Request failed during generation: Server error: Can't find 'adapter_config.json' at '/data/models--s3:----adapters--gsm8k/snapshots'

The adapter is getting downloaded to models--{model_id}/snapshots folder. But get_local_path is returning path "/data/models--s3:----{bucket}--{model_id}/snapshots".

This fix returns the "models--{model_id}/snapshots" path

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Was this discussed/approved via a Github issue or the discord / slack channel? Please add a link
  to it if that's the case.
• Did you write any new necessary tests?

Who can review?

@tgaddair

[tgaddair]

Good catch! This is definitely an oversight when we introduced the _get_bucket_and_model_id helper.

CI is failing due to a Rust dep, which is a known issue, so I'll land this as is for now.