Remove dev branch dependencies from dev requirements

[mikealfare]

Problem

We were pulling in dbt-adapters from main on GH and made a breaking change.

Solution

Since 1.8 is a final release, we should not be pulling from dev branches for tests. Remove all dbt dependencies from GitHub. Leave dbt-tests-adapter but pull it from PyPI.

Checklist

• [x] I have read the contributing guide and understand what's expected of me
• [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] 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

[github-actions[bot]]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-snowflake contributing guide.

[mikealfare]

We are going to update the unit tests instead.