Remove cumulative metric type param deprecation warning

[DevonFulcher]

Description

This PR removes a deprecation warning so that it can be moved into dbt-core as a behavior change.

Checklist

• [x] I have read the contributing guide and understand what's expected of me
• [x] I have signed the CLA
• [x] This PR includes tests, or tests are not required/relevant for this PR
• [x] I have run changie new to create a changelog entry