package/collectd: remove libvirt from list of disabled plugins

package/collectd: remove libvirt from list of disabled plugins

With collectd 5.5.0 the "libvirt plugin has been renamed to virt":
https://git.octo.it/?p=collectd.git;a=blob;f=ChangeLog;h=b0a997c53ac1a74bc39470bdd243f853fa095c9f;hb=refs/tags/collectd-5.5.0#l235

"virt" is already mentioned in COLLECTD_PLUGINS_DISABLE so we can just
remove "libvirt" to fix:

configure: WARNING: unrecognized options: [...] --disable-libvirt

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>