Fix a debug log about the Athena workgroup

[dtaniwaki]

resolves #1210
docs dbt-labs/docs.getdbt.com/#

Problem

The Athena adapter emits a debug log as below by mistake.

09:00:09  dbt.adapters.athena.constants adapter: get_work_group for %s

Solution

Fixed the log.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

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