[pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/kynan/nbstripout: 0.7.1 → 0.8.1](https://github.com/kynan/nbstripout/compare/0.7.1...0.8.1)

.pre-commit-config.yaml

@@ -1,6 +1,6 @@
 repos:
   - repo: https://github.com/kynan/nbstripout
-    rev: 0.7.1
+    rev: 0.8.1
     hooks:
     - id: nbstripout
       files: ".ipynb"