[pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/asottile/pyupgrade: v3.20.0 → v3.21.0](asottile/pyupgrade@v3.20.0...v3.21.0)

Author: pre-commit-ci[bot]

.pre-commit-config.yaml

@@ -5,7 +5,7 @@ repos:
     -   id: trailing-whitespace
         files: ^moha/.*\.py$
 -   repo: https://github.com/asottile/pyupgrade
-    rev: v3.20.0
+    rev: v3.21.0
     hooks:
     -   id: pyupgrade
         args: [--py36-plus]