gitweb: Fix typo in run() subroutine

Run $post_dispatch_hook->() not $pre_dispatch_hook->() after each
request.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -1125,7 +1125,7 @@ sub run {
 
 		run_request();
 
-		$pre_dispatch_hook->()
+		$post_dispatch_hook->()
 			if $post_dispatch_hook;
 
 		last REQUEST if ($is_last_request->());