kbd-model-map: add a mapping for switched czech qwerty/us

kbd-model-map: add a mapping for switched czech qwerty/us

See https://bugzilla.redhat.com/show_bug.cgi?id=2121106 for the
background on this. One of Fedora's QA folks ran an install
and chose two keyboard layouts: Czech (qwerty) and US. Due to
the sad details of how the whole logic flow for trying to decide
what kbd layout best matches a given xkb config works (see
details in the bug comments), we wound up deciding the best-
matching kbd layout for this situation was cz-us-qwertz, which
is a czech/us switched layout, but is qwertz, not qwerty. This
seems like a poor outcome. Adding this line should result in us
picking cz-qwerty in this case. Which may be the 'legacy'
cz-qwerty.map from upstream kbd project (which is switched
cz/us), or may be the auto-converted xkb layout (which obviously
isn't switched). But either way, at least its primary mode is
Czech qwerty, which seems like a *better* choice than a layout
whose primary mode is Czech qwertz.

Signed-off-by: Adam Williamson <awilliam@redhat.com>