Add an additional grammar change to the listener option

modules/auxiliary/spoof/arp/arp_poisoning.rb

@@ -35,7 +35,7 @@ class Metasploit3 < Msf::Auxiliary
       OptString.new('INTERFACE', 	[false, 'The name of the interface']),
       OptBool.new(  'BIDIRECTIONAL',	[true, 'Spoof also the source with the dest',false]),
       OptBool.new(  'AUTO_ADD',	[true, 'Auto add new host when discovered by the listener',false]),
-      OptBool.new(  'LISTENER',    	[true, 'Use an additional thread that will listen to arp request and try to reply as fast as possible', true])
+      OptBool.new(  'LISTENER',    	[true, 'Use an additional thread that will listen for arp requests to reply as fast as possible', true])
     ], self.class)
 
     register_advanced_options([