timer: remove duplicated word in comment

PR-URL: nodejs#11323
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>

lib/timers.js

@@ -15,7 +15,7 @@ const TIMEOUT_MAX = 2147483647; // 2^31-1
 //
 // Timers are crucial to Node.js. Internally, any TCP I/O connection creates a
 // timer so that we can time out of connections. Additionally, many user
-// user libraries and applications also use timers. As such there may be a
+// libraries and applications also use timers. As such there may be a
 // significantly large amount of timeouts scheduled at any given time.
 // Therefore, it is very important that the timers implementation is performant
 // and efficient.