ci: update pre-commit (#488)

Caching is now internal! Much nicer.

.github/workflows/tests.yml

@@ -15,13 +15,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - uses: actions/setup-python@v2
-    - name: set PY
-      run: echo "::set-env name=PY::$(python -c 'import hashlib, sys;print(hashlib.sha256(sys.version.encode()+sys.executable.encode()).hexdigest())')"
-    - uses: actions/cache@v1
-      with:
-        path: ~/.cache/pre-commit
-        key: pre-commit|${{ env.PY }}|${{ hashFiles('.pre-commit-config.yaml') }}
-    - uses: pre-commit/action@v1.1.0
+    - uses: pre-commit/action@v2.0.0
 
   cuda-build:
     name: CUDA build only