Update README.md

In 2020, the concept of a single compose specification was introduced, removing the need for versioning.

README.md

@@ -56,7 +56,6 @@ I won't go in to too much detail here but here are the basics for someone new to
 2. Create a docker-compose.yml file similar to this:
 
 ```yml
-version: '3.8'
 services:
   app:
     image: 'docker.io/jc21/nginx-proxy-manager:latest'