Updated README.md to make setup examples consistent

- SSH and apt examples should use same username

README.md

@@ -206,13 +206,13 @@ ssh:
   user: app
 ```
 
-If you are using non-root user, you need to bootstrap your servers manually, before using them with MRSK. On Ubuntu, you'd do:
+If you are using non-root user (`app` as above example), you need to bootstrap your servers manually, before using them with MRSK. On Ubuntu, you'd do:
 
 ```bash
 sudo apt update
 sudo apt upgrade -y
 sudo apt install -y docker.io curl git
-sudo usermod -a -G docker ubuntu
+sudo usermod -a -G docker app
 ```
 
 ### Using a proxy SSH host