xwayland/eglstream: Drop xwl_eglstream_set_window_pixmap

Not sure why we'd need to abandon a pending stream for a pixmap just
because it's no longer a window pixmap. Let's try not to.

Reviewed-by: Olivier Fourdan <ofourdan@redhat.com>
5 jobs for xwl_eglstream_set_window_pixmap-sayonara in 6 minutes and 54 seconds (queued for 57 seconds)
Status Job ID Name Coverage
  Docker Image
passed debian-buster #11666457

00:00:16

 
  Build And Test
passed autotools #11666458

00:06:37

passed meson #11666459

00:02:42

passed meson-noglamor #11666460

00:01:38

passed mingw-cross-build #11666461

00:00:42