doc: remove extra whitespace in module docs

PR-URL: https://github.com/nodejs/node/pull/17711
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>

doc/api/modules.md

@@ -838,7 +838,7 @@ added: v9.3.0
 
 * {string[]}
 
-A list of  the names of all modules provided by Node.js. Can be used to verify
+A list of the names of all modules provided by Node.js. Can be used to verify
 if a module is maintained by a third-party module or not.
 
 [`__dirname`]: #modules_dirname