[lib] Remove extraneous space in thread creation robotext

Summary: Noticed the extraneous space when I received a notif.

Test Plan: N/A

Reviewers: rohan, varun, atul

Reviewed By: rohan, atul

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D8734

lib/shared/notif-utils.js

@@ -168,7 +168,7 @@ function notifTextsForSidebarCreation(
     possessive: true,
   });
 
-  let body = `started a thread in response to `;
+  let body = 'started a thread in response to';
   body = ET`${body} ${sourceMessageAuthorPossessive} message`;
 
   const { username } = params.notifTargetUserInfo;