Fixed tiers resetting in Ember when created in AdminX (#18554)

refs https://github.com/TryGhost/Product/issues/3832

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### <samp>🤖 Generated by Copilot at 3fbb5c5</samp>

Reload members data when tiers settings change. This ensures that the UI
shows the correct counts and labels of the tiers after updating them in
the settings component.

ghost/admin/app/components/admin-x/settings.js

@@ -374,6 +374,11 @@ export default class AdminXSettings extends Component {
         }
 
         run(() => this.store.unloadAll(type));
+
+        if (dataType === 'TiersResponseType') {
+            // membersUtils has local state which needs to be updated
+            this.membersUtils.reload();
+        }
     };
 
     onDelete = (dataType, id) => {