fixed small typo

changed uprate to upgrade on line 12

Author: tedleyem

content/en/docs/setup/production-environment/_index.md

@@ -9,7 +9,7 @@ no_list: true
 A production-quality Kubernetes cluster requires planning and preparation.
 If your Kubernetes cluster is to run critical workloads, it must be configured to be resilient.
 This page explains steps you can take to set up a production-ready cluster,
-or to uprate an existing cluster for production use.
+or to upgrade an existing cluster for production use.
 If you're already familiar with production setup and want the links, skip to
 [What's next](#what-s-next).