pre-commit: set clang-format to v12 and Google style

.pre-commit-config.yaml

 repos:
 -   repo: https://github.com/pre-commit/mirrors-clang-format
-    rev: 'v13.0.1'  # Use the sha / tag you want to point at
+    rev: v12.0.1
     hooks:
     -   id: clang-format
+        args: [--style=Google]
 -   repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v2.3.0
     hooks: