doc: fix typo in http.md

`closed` -> `close`.

Author: lpinca

doc/api/http.md

@@ -1364,7 +1364,7 @@ before closing keep alive connection.
 
 A value of `null` will disable the limit.
 
-When limit is reach it will set `Connection` header value to `closed`,
+When limit is reach it will set `Connection` header value to `close`,
 but will not actually close the connection, subsequent requests sent
 after the limit is reached will get `503 Service Unavailable` as a response.