Fix setting name reference

docs/topics/extensions.rst

@@ -280,7 +280,7 @@ An integer which specifies a number of items. If the spider scrapes more than
 that amount and those items are passed by the item pipeline, the
 spider will be closed with the reason ``closespider_itemcount``.
 Requests which  are currently in the downloader queue (up to
-:setting:`CONCURRENT_REQUEST` requests) are still processed. 
+:setting:`CONCURRENT_REQUESTS` requests) are still processed. 
 If zero (or non set), spiders won't be closed by number of passed items.
 
 .. setting:: CLOSESPIDER_PAGECOUNT