Remove pre-commit workflow.

Fixes #397

.github/workflows/pre-commit.yml

@@ -1,24 +0,0 @@
-name: pre-commit
-
-on:
-  push:
-    branches:
-      - main
-  pull_request:
-
-jobs:
-  pre-commit:
-    runs-on: ubuntu-20.04
-
-    steps:
-      - uses: actions/checkout@v2
-        with:
-          fetch-depth: 0
-
-      - uses: actions/setup-python@v2
-        with:
-          python-version: 3.9
-
-      - uses: pre-commit/action@v2.0.0
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}