Fixed module name in comment. It was forgotten in r4281.

src/http/ngx_http_request.h

diff --git a/src/http/ngx_http_request.h b/src/http/ngx_http_request.h
index 220aa13..108dba9 100644
--- a/src/http/ngx_http_request.h
+++ b/src/http/ngx_http_request.h
@@ -478,7 +478,7 @@
 
     /*
      * instead of using the request context data in
-     * ngx_http_limit_zone_module and ngx_http_limit_req_module
+     * ngx_http_limit_conn_module and ngx_http_limit_req_module
      * we use the single bits in the request structure
      */
     unsigned                          limit_conn_set:1;