refactor: update subject tests. extract common user logic

Author: setchy

src/utils/subject.ts

@@ -203,11 +203,9 @@ async function getLatestCommentUser(
   notification: Notification,
   token: string,
 ): Promise<User> {
-  const response: IssueComments | ReleaseComments = (
+  const response: IssueComments = (
     await apiRequestAuth(notification.subject.latest_comment_url, 'GET', token)
   ).data;
 
-  return (
-    (response as IssueComments).user ?? (response as ReleaseComments).author
-  );
+  return response.user;
 }