should not pick up alpha versions

Author: bsipocz

.pre-commit-config.yaml

@@ -29,7 +29,7 @@ repos:
       - id: blacken-docs
 
   - repo: https://github.com/pre-commit/mirrors-prettier
-    rev: f12edd9c7be1c20cfa42420fd0e6df71e42b51ea # frozen: v4.0.0-alpha.8
+    rev: ffb6a759a979008c0e6dff86e39f4745a2d9eac4 # frozen: v3.1.0
     hooks:
       - id: prettier
         files: \.(css|html|md|yml|yaml)