Renamed "client" references to "admin"

refs: https://github.com/TryGhost/Toolbox/issues/299

- renamed things that reference Ghost admin as "client"
- these things make even less sense in a post core/client world

ghost/admin/Gruntfile.js

@@ -64,7 +64,7 @@ module.exports = function (grunt) {
         }
     });
 
-    grunt.registerTask('init', 'Install the client dependencies',
+    grunt.registerTask('init', 'Install the admin dependencies',
         ['shell:npm-install']
     );
 };

ghost/admin/README.md

@@ -2,7 +2,7 @@
 
 ![](https://github.com/TryGhost/Admin/workflows/Test%20Suite/badge.svg?branch=main)
 
-This is the home of Ember.js based admin client that ships with [Ghost](https://github.com/tryghost/ghost).
+This is the home of Ember.js based admin app that ships with [Ghost](https://github.com/tryghost/ghost).
 
 **Do you want to set up a Ghost blog?** Check the [getting started guide](https://ghost.org/docs/introduction/)
 
@@ -10,7 +10,7 @@ This is the home of Ember.js based admin client that ships with [Ghost](https://
 
 ## Have a bug or issue?
 
-Bugs and issues (even if they only affect the admin client) should be opened on the core [Ghost](https://github.com/tryghost/ghost/issues) repository.
+Bugs and issues (even if they only affect the admin app) should be opened on the core [Ghost](https://github.com/tryghost/ghost/issues) repository.
 
 # Copyright & License
 

ghost/admin/app/README.md

@@ -1,4 +1,4 @@
-# Ghost Admin Client
+# Ghost Admin App
 
 Ember.js application used as a client-side admin for the [Ghost](http://ghost.org) blogging platform. This readme is a work in progress guide aimed at explaining the specific nuances of the Ghost Ember app to contributors whose main focus is on this side of things.