Increase a send_errors test timeout

Depending on the environment the send buffer may not be
configured as low as we want, so the test will take longer.

Author: essen

test/send_errors_SUITE.erl

@@ -89,7 +89,7 @@ http2_send_ping_fail(_) ->
 			gun:close(Pid);
 		Msg ->
 			error({fail, Msg})
-	after 5000 ->
+	after 15000 ->
 		error(timeout)
 	end.