Removed unused confirm-leave handling from theme settings screen

no issue

- appears to be left-over from copy/paste of an earlier screen re-structure
- cleaning up for easier extraction of functionality to new screens / modals

ghost/admin/app/routes/settings/theme.js

@@ -23,12 +23,6 @@ export default AuthenticatedRoute.extend(CurrentUserSettings, {
         this.controller.send('reset');
     },
 
-    deactivate() {
-        this._super(...arguments);
-        this.controller.set('leaveSettingsTransition', null);
-        this.controller.set('showLeaveSettingsModal', false);
-    },
-
     actions: {
         activateTheme(theme) {
             return this.controller.send('activateTheme', theme);

ghost/admin/app/templates/settings/theme.hbs

@@ -7,13 +7,6 @@
         </h2>
     </GhCanvasHeader>
 
-    {{#if this.showLeaveSettingsModal}}
-        <GhFullscreenModal @modal="leave-settings"
-            @confirm={{action "leaveSettings"}}
-            @close={{action "toggleLeaveSettingsModal"}}
-            @modifier="action wide" />
-    {{/if}}
-
     <section class="view-container">
         <div class="gh-setting-header gh-first-header flex justify-between">
             <span>Ghost theme directory</span>