🐛 Fixed code card not correctly saving language when changing

closes https://github.com/TryGhost/Team/issues/1662

- the on-blur action for the language input was modifying the language property in the payload object directly which meant that the mobiledoc `save` call was missing and all the associated editor behaviour for serializing and saving the update was lost
- switched to modern action syntax and a proper action on the backing component so we're saving the change correctly

ghost/admin/lib/koenig-editor/addon/components/koenig-card-code.hbs

@@ -31,7 +31,7 @@
         <input
             type="text"
             value={{readonly this.payload.language}}
-            onblur={{action (mut this.payload.language) value="target.value"}}
+            {{on "blur" this.updateLanguage}}
             placeholder="Language..."
             class="absolute w-20 pa1 ba b--lightgrey br2 f8 tracked-2 fw4 z-999 outline-0 anim-normal"
             style={{this.languageInputStyle}}

ghost/admin/lib/koenig-editor/addon/components/koenig-card-code.js

@@ -117,6 +117,11 @@ export default class KoenigCardCode extends Component {
         this._updatePayloadAttr('caption', caption);
     }
 
+    @action
+    updateLanguage(event) {
+        this._updatePayloadAttr('language', event.target.value);
+    }
+
     @action
     enterEditMode() {
         this._addMousemoveHandler();