update changelog

app/assets/javascripts/smart_interval.js

@@ -116,7 +116,7 @@ export default class SmartInterval {
       })
       .catch((err) => {
         this.isLoading = false;
-        throw new Error(err);
+        throw err;
       });
   }
 

changelogs/unreleased/38394-smarter-interval.yml

 ---
-title: improve merge request realtime polling performance
-merge_request:
+title: Update Merge Request polling so there is only one request at a time
+merge_request: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/15032
 author:
 type: fixed