Fix a typo in kpt book (#3141)

Author: cartyc

site/book/08-package-orchestration/01-system-requirements.md

@@ -1,6 +1,6 @@
 In order to follow the packge orchestration examples, you will need:
 
-* the Package Orchestration servie (Porch)
+* the Package Orchestration service (Porch)
   [installed](https://kpt.dev/guides/porch-installation) in your Kubernetes
   cluster and [kubectl context][kubeconfig] configured with your cluster.
 * kpt CLI [installed](/installation/) on your system