compositor-x11: remove redundant state arg of x11_backend_deliver_button_event
compositor-x11: remove redundant state arg of x11_backend_deliver_button_event

The "state" variable in x11_backend_deliver_button_event is basically the
same as (event->response_type == XCB_BUTTON_PRESS), thus update the code
to use the last one.

Signed-off-by: Benoit Gschwind <6d0fcc95e39ab8ccb88bafebb2075e9d5c92b713@gnu-log.net>
Reviewed-by: Daniel Stone <62e7e355d5d8400fa8384448796af0bf6be4ffae@collabora.com>
Reviewed-by: Quentin Glidic <241385a0e41ea713327e189bce1062decf7c1eb5@sardemff7.net>

krezovic/weston,sir-murray/weston,sir-murray/weston,krezovic/weston