chore(job_attachments): remove service model file

[gahyusuh]

What was the problem/requirement? (What/Why)

This package previously had a copy of the service model file (JSON) for use in these unit tests and by GitHub Checks to access the boto3 deadline client's stubber fixture. The service model file was at data/boto_module/deadline/1989-09-22/service.json. This setup seemed unnecessary for several reasons:

• The get_queue() in (_aws/deadline.py) has already been covered multiple times in integration tests, so it seemed unnecessary to test it in unit tests by patching the service model file directly.
• We don't have a reliable mechanism to keep this copy of service model file up-to-date, especially considering it hadn't been updated in the past four months.

What was the solution? (How)

• Removed the service model file from the package.
• Refactored the unit tests that depended on this file, implementing mocks to ensure they still pass without needing to access the service model file.

What is the impact of this change?

Remove unnecessary dependencies and potential points of failure due to out-of-date service model.

How was this change tested?

Confirmed that all unit tests and integration tests (for job attachments) were passing.

Was this change documented?

No.

Is this a breaking change?

No.