Remove duplicate .pre-commit-*.yml files (#1089)

Identical .yaml copies are still in place.

Before:
> # ls -1 .pre-commit-*.y*
> .pre-commit-config.yaml
> .pre-commit-config.yml
> .pre-commit-hooks.yaml
> .pre-commit-hooks.yml

After:
> # ls -1 .pre-commit-*.y*
> .pre-commit-config.yaml
> .pre-commit-hooks.yaml
2 files changed