Remove `ember-web-app-rename` removal from after install hook

[Jan Bobisud]

Is this still needed to be handled here? 🤔

https://github.com/zonkyio/ember-web-app/blob/master/blueprints/ember-web-app/index.js#L13

Should be https://github.com/san650/ember-web-app-rename deprecated itself and users will be notified to update ember-web-app from that add-on?

/cc @san650

[Santiago Ferreira]

@bobisjan I think it's safe now to remove that logic. I'll deprecate ember-web-app-rename, good call.