refactor(@angular/cli): remove v1 postinstall update check

This postinstall script was put in place during the v6.0 timeframe to aid users migrating from the v1.x configuration file format by displaying a message instructing the user to run `ng update`.
The `ng update` migration is still functional and users can still use it to migrate from a v1.x project.  However, the postinstall script will no longer be run for every install of the Angular CLI.

Author: clydin

packages/angular/cli/bin/postinstall/ng-update-message.js

@@ -3,6 +3,5 @@
 
 // These should not fail but if they do they should not block installation of the package
 try {
-  require('./ng-update-message');
   require('./analytics-prompt');
 } catch (_) {}