update package examples to book (#3197)

Author: Mengqi Yu

package-examples/nginx/deployment.yaml

@@ -28,7 +28,7 @@ spec:
     spec:
       containers:
         - name: nginx
-          image: "nginx:1.16.1"
+          image: "nginx:1.18.0"
           ports:
             - protocol: TCP
               containerPort: 80

package-examples/wordpress/deployment/volume.yaml

@@ -20,6 +20,6 @@ metadata:
 spec:
   resources:
     requests:
-      storage: 3Gi
+      storage: 4Gi
   accessModes:
     - ReadWriteOnce