drop several entries from kbd-model-map whose kbd layouts do not exist

drop several entries from kbd-model-map whose kbd layouts do not exist

kbd-model-map was generated from system-config-keyboard's keyboard_models.py.
Several of the kbd layouts referred in that file do not exist and, so far as I
can tell, never did. I believe these entries existed simply to provide the xkb
configuration information for those layouts, and there never were matching kbd
entries; the kbd names were entirely notional, to satisfy the need for some
entry or other in that field.

For systemd, the only function of kbd-model-map is to 'match' kbd and xkb
configurations, so it does not make any sense to maintain entries for cases
where only one or the other exists in this context.