glx: drop always-true #ifdef

Meson already guarantees we have at least xdamage >= 1.1

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5862>
1 file changed