Change repo for the prettier pre-commit hook

Per https://github.com/prettier/prettier/issues/9459 and specifically
https://github.com/prettier/prettier/issues/9459#issuecomment-713223710
the prettier hook for pre-commit is being broken out into its own repo.

.pre-commit-config.yaml

@@ -93,8 +93,8 @@ repos:
     rev: v2.0.0
     hooks:
       - id: docker-compose-check
-  - repo: https://github.com/prettier/prettier
-    rev: 2.1.2
+  - repo: https://github.com/prettier/pre-commit
+    rev: v2.1.2
     hooks:
       - id: prettier
   - repo: https://github.com/pre-commit/mirrors-mypy