Move autosize from admin/lib to discourse/lib

.eslintignore

@@ -7,7 +7,7 @@ app/assets/javascripts/vendor.js
 app/assets/javascripts/locales/i18n.js
 app/assets/javascripts/defer/html-sanitizer-bundle.js
 app/assets/javascripts/ember-addons/
-app/assets/javascripts/admin/lib/autosize.js.es6
+app/assets/javascripts/discourse/lib/autosize.js.es6
 lib/javascripts/locale/
 lib/javascripts/messageformat.js
 lib/javascripts/moment.js

app/assets/javascripts/admin/components/expanding-text-area.js.es6

@@ -1,5 +1,5 @@
 import { on, observes } from 'ember-addons/ember-computed-decorators';
-import autosize from 'admin/lib/autosize';
+import autosize from 'discourse/lib/autosize';
 
 export default Ember.TextArea.extend({
   @on('didInsertElement')