[pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/adamchainz/blacken-docs: 1.19.1 → 1.20.0](adamchainz/blacken-docs@1.19.1...1.20.0)

Author: pre-commit-ci[bot]

.pre-commit-config.yaml

@@ -6,7 +6,7 @@ repos:
   - id: black
 
 - repo: https://github.com/adamchainz/blacken-docs
-  rev: 1.19.1
+  rev: 1.20.0
   hooks:
   - id: blacken-docs
     additional_dependencies: [black==23.12.1]