rpm: drop dependency on now obsolete qubes-core-dom0-doc package

rpm_spec/core-dom0.spec

@@ -83,7 +83,6 @@ Requires:       libvirt-python3
 
 Requires:       pciutils
 Requires:       qubes-core-dom0-linux >= 3.1.8
-Requires:       qubes-core-dom0-doc
 Requires:       qubes-db-dom0
 # TODO: R: qubes-gui-dom0 >= 2.1.11
 Conflicts:      qubes-gui-dom0 < 1.1.13