[minor] Fix typo (#1929)

Author: eltociear

lib/receiver.js

@@ -427,7 +427,7 @@ class Receiver extends Writable {
 
     if (data.length) {
       //
-      // This message is not compressed so its lenght is the sum of the payload
+      // This message is not compressed so its length is the sum of the payload
       // length of all fragments.
       //
       this._messageLength = this._totalPayloadLength;