Fix: Update service.md (nginx image not found)

I fixed an imagepulling error in the service.md example on the website. nginx:11.14.2 is no longer on Nginx docker hub:  https://hub.docker.com/_/nginx?tab=tags&page=1&name=11.14.2 so I changed the image tag to the latest. please let me know if the latest tag is not the right image to use or if I'm wrong.

Author: adeniyistephen

content/en/docs/concepts/services-networking/service.md

@@ -122,7 +122,7 @@ metadata:
 spec:
   containers:
   - name: nginx
-    image: nginx:11.14.2
+    image: nginx:latest
     ports:
       - containerPort: 80
         name: http-web-svc