control: Drop dependency on radvd

libvirt only needed radvd together with old dnsmasq versions,
but the minimum dnsmasq version is now new enough for the
dependency to no longer be necessary.

debian/control

@@ -60,7 +60,6 @@ Build-Depends:
  python3:any,
  qemu-system-common,
  qemu-utils,
- radvd [linux-any],
  systemtap-sdt-dev [linux-any],
  xsltproc,
 Vcs-Git: https://salsa.debian.org/libvirt-team/libvirt.git
@@ -352,7 +351,6 @@ Suggests:
  nfs-common,
  open-iscsi [linux-any],
  pm-utils,
- radvd,
  systemd,
  systemtap,
  zfsutils,