XdgShellv5 and XdgShellv6 have been deprecated in
the compositor since 5.15, and wl-scaler since 5.13.
These are now removed.

Since the qwindow-compositor has not been updated
for a long time, it depends on the outdated protocols.
This change removes it, since it no longer represents
best practices. This means we will be missing a proper
C++-based compositor for now, so we will have to
create a new one later.

Change-Id: Icc6ef97c17e553f266c4145abeef26ddd631d6bf
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>