Rename /api/v2_alpha/notifications* to /api/v2/notifications* (#31840)

app/javascript/mastodon/api/notifications.ts

@@ -37,7 +37,7 @@ export const apiFetchNotificationGroups = async (params?: {
 }) => {
   const response = await api().request<ApiNotificationGroupsResultJSON>({
     method: 'GET',
-    url: '/api/v2_alpha/notifications',
+    url: '/api/v2/notifications',
     params,
   });