[pre-commit.ci] pre-commit autoupdate (#983)

<!--pre-commit.ci start-->
updates:
- [github.com/asottile/blacken-docs: v1.12.1 →
1.13.0](adamchainz/blacken-docs@v1.12.1...1.13.0)
<!--pre-commit.ci end-->

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: pre-commit-ci[bot]

.pre-commit-config.yaml

@@ -29,7 +29,7 @@ repos:
   hooks:
   - id: black
 - repo: https://github.com/asottile/blacken-docs
-  rev: v1.12.1
+  rev: 1.13.0
   hooks:
   - id: blacken-docs
     additional_dependencies: