setcap on kwin

[Harald Sitter]

...do we still need and want it?

It gets in the way of crash tracking because it results in
kwin_wayland crashes getting special protection by coredumpd that make
the cores unreadable for the user [1][2][3]. So we either need polkit
elevation in drkonqi or drop the setcap stuff.

Opinions?

[1] gran_user_access
https://github.com/systemd/systemd/blob/f7f842f88850414d1cdb4918c1feba212df5eca1/src/coredump/coredump.c#L351
[2] parse_auxv https://github.com/systemd/systemd/blob/f7f842f88850414d1cdb4918c1feba212df5eca1/src/shared/coredump-util.c#L71
[3] AT_SECURE https://man7.org/linux/man-pages/man3/getauxval.3.html