Remove CI badge

It hasn't been getting updated and you can always see the latest GitHub
Action status where GitHub shows the latest commit.

Author: nickjj

README.md

@@ -1,7 +1,5 @@
 # An example Node + Docker app
 
-![CI](https://github.com/nickjj/docker-node-example/workflows/CI/badge.svg?branch=main)
-
 You could use this example app as a base for your new project or as a guide to
 Dockerize your existing Node app.