Remove qmake from the project

qmake without qt is minimally usefull. Moreover providing qt in
only public-stack would mean it's never tested in our CI which makes
its support questionable. Providing qt in flatpak sdk was ruled
out after discussion with KDE developers.

Considering all of above, the best solution may be removing qmake
from the project.See [1] and below for more context.

!647 (comment 113757590)
10 jobs for EmersonBernier/remove_qmake in 58 minutes and 51 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Flatpak
passed #261920552
aarch64
app_aarch64

00:55:46

passed #261920553
armhf
app_arm

00:35:00

passed #261920550
cache_i686 x86_64
app_i686

00:56:21

passed #261920555
ppc64le allowed to fail
app_powerpc64le

00:27:53

passed #261920548
cache_x86_64 x86_64
app_x86_64

00:55:51

 
  Vm
manual #261920562
aarch64 allowed to fail manual
minimal_systemd_vm_aarch64
passed #261920564
armhf
minimal_systemd_vm_arm

00:02:28

passed #261920559
cache_i686 x86_64
minimal_systemd_vm_i686

00:01:53

manual #261920566
ppc64le allowed to fail manual
minimal_systemd_vm_powerpc64le
passed #261920557
cache_x86_64 x86_64
minimal_systemd_vm_x86_64

00:01:22