doc: remove extra space on threadpool usage

PR-URL: nodejs/node#44734
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/fs.md

@@ -7233,7 +7233,7 @@ try {
 
 ### Threadpool usage
 
-All callback and promise-based file system APIs ( with the exception of
+All callback and promise-based file system APIs (with the exception of
 `fs.FSWatcher()`) use libuv's threadpool. This can have surprising and negative
 performance implications for some applications. See the
 [`UV_THREADPOOL_SIZE`][] documentation for more information.