http: remove duplicate comment

A comment explaining kOnHeaders function of the parser was duplicated
in two places but the second instance was more confusing than helpful.

PR-URL: #20126
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

lib/_http_common.js

@@ -159,11 +159,6 @@ const parsers = new FreeList('parsers', 1000, function() {
   parser.incoming = null;
   parser.outgoing = null;
 
-  // Only called in the slow case where slow means
-  // that the request headers were either fragmented
-  // across multiple TCP packets or too large to be
-  // processed in a single run. This method is also
-  // called to process trailing HTTP headers.
   parser[kOnHeaders] = parserOnHeaders;
   parser[kOnHeadersComplete] = parserOnHeadersComplete;
   parser[kOnBody] = parserOnBody;