Disable pre-commit hooks

Summary:
These are broken on 2.7 (https://github.com/dagster-io/dagster/issues/1464) and the black
pre-commit hook handles command-line flags in a way that is inconsistent with other invocations --
given that vscode is adequate for day-to-day dev and we also run black in CI, simpler just to
remove.

Test Plan: Manual

Reviewers: schrockn, alangenfeld, natekupp

Reviewed By: natekupp

Differential Revision: https://dagster.phacility.com/D558