[pre-commit.ci] pre-commit autoupdate

updates:
- [github.com/asottile/pyupgrade: v2.26.0 → v2.28.0](asottile/pyupgrade@v2.26.0...v2.28.0)

Author: pre-commit-ci[bot]

.pre-commit-config.yaml

@@ -23,7 +23,7 @@ repos:
       - id: isort
         name: isort (python)
   - repo: https://github.com/asottile/pyupgrade
-    rev: v2.26.0
+    rev: v2.28.0
     hooks:
     -   id: pyupgrade
         args: [--py37-plus]