doc: fixing minor typo in AtExit hooks section

PR-URL: https://github.com/nodejs/node/pull/7485
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

doc/api/addons.md

@@ -1019,7 +1019,7 @@ console.log(result); // 30
 ### AtExit hooks
 
 An "AtExit" hook is a function that is invoked after the Node.js event loop
-has ended by before the JavaScript VM is terminated and Node.js shuts down.
+has ended but before the JavaScript VM is terminated and Node.js shuts down.
 "AtExit" hooks are registered using the `node::AtExit` API.
 
 #### void AtExit(callback, args)