Fix typo in development guide (GoogleCloudPlatform#449)

Hi there,
as title says
Didier

docs/development-guide.md

@@ -79,7 +79,7 @@ gcloud services enable monitoring.googleapis.com \
 
     - To launch **Minikube** (tested with Ubuntu Linux). Please, ensure that the
        local Kubernetes cluster has at least:
-        - 4 CPU's
+        - 4 CPUs
         - 4.0 GiB memory
         - 32 GB disk space
 
@@ -125,4 +125,4 @@ gcloud services enable monitoring.googleapis.com \
 ## Cleanup
 
 If you've deployed the application with `skaffold run` command, you can run
-`skaffold delete` to clean up the deployed resources.
+`skaffold delete` to clean up the deployed resources.