Prep for 1.8.7 release

[benc-db]

Description

Perpares for 1.8.7 release; only notable change is that we stop running cluster by None.

Checklist

• [x] I have run this code in development and it appears to resolve the stated issue
• [x] This PR includes tests, or tests are not required/relevant for this PR
• [x] I have updated the CHANGELOG.md and added information about my change to the "dbt-databricks next" section.