Update pre-commit hook gruntwork-io/pre-commit to v0.1.21

.pre-commit-config.yaml

@@ -6,6 +6,6 @@ repos:
 #     args: [--allow-multiple-documents]
 #     exclude: \*./charts/base/templates
 - repo: https://github.com/gruntwork-io/pre-commit
-  rev: v0.1.20
+  rev: v0.1.21
   hooks:
   - id: helmlint