DEPS: update pyupgrade for py38 syntax (pandas-dev#42392)

Author: fangchenli

.pre-commit-config.yaml

@@ -60,7 +60,7 @@ repos:
     rev: v2.20.0
     hooks:
     -   id: pyupgrade
-        args: [--py37-plus]
+        args: [--py38-plus]
 -   repo: https://github.com/pre-commit/pygrep-hooks
     rev: v1.9.0
     hooks: