Update pre-commit hook asottile/pyupgrade to v3.21.0

Author: renovate[bot]

.pre-commit-config.yaml

@@ -11,7 +11,7 @@ repos:
       - id: check-merge-conflict
   # Pyupgrade: upgrades older python syntax to newer one
   - repo: https://github.com/asottile/pyupgrade
-    rev: v3.20.0
+    rev: v3.21.0
     hooks:
     - id: pyupgrade
       args: ["--py38-plus"]