Ignore dpms status in Display::outputsIntersecting()

Display::outputsIntersecting() is used to compute the list of outputs
where the given surface is. The problem is that it accounts for the dpms
mode.

This means that if an output is turned off, clients will receive a leave
event and they may potentially decide to change the buffer scale and
commit new buffers.

The dpms check was introduced to fix a crash, however since then, output
bits in kwin have changed drastically, in particular how wl_output
objects are destroyed. So, it should be safe to remove the dpms check.