[pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/rbubley/mirrors-prettier: 4923370d55631aa5b66f612f52d67b2e0ca2a38c → 39e2973981e6d2f9b6c543b0086a2d2393abdc89](rbubley/mirrors-prettier@4923370...39e2973)

Author: pre-commit-ci[bot]

.pre-commit-config.yaml

@@ -24,7 +24,7 @@ repos:
       - id: blacken-docs
 
   - repo: https://github.com/rbubley/mirrors-prettier
-    rev: 4923370d55631aa5b66f612f52d67b2e0ca2a38c # frozen: v3.9.1
+    rev: 39e2973981e6d2f9b6c543b0086a2d2393abdc89  # frozen: v3.9.4
     hooks:
       - id: prettier
         files: \.(css|md|yml|yaml)