[pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/asottile/blacken-docs: 1.16.0 → 1.18.0](adamchainz/blacken-docs@1.16.0...1.18.0)

.pre-commit-config.yaml

@@ -78,4 +78,4 @@ repos:
   - hooks:
       - id: blacken-docs
     repo: https://github.com/asottile/blacken-docs
-    rev: 1.16.0
+    rev: 1.18.0