[ci] Remove disabled packages from the RPMs list.

[ci] Remove disabled packages from the RPMs list.

The following packages are no longer built when creating the RPMs for collectd:

* collectd-gps - not buildable on RHEL8
* collectd-lvm - lvmlvapp was deprecated upstream
* collectd-modbus - not buildable on RHEL8
* collectd-mqtt - not buildable on RHEL8
* collectd-nut - dependencies deprecated upstream
* collectd-ping - not buildable on RHEL 8
* collectd-smart - only buildable on RHEL 7
* collectd-varnish - dependencies deprecated upstream

Change-Id: I3d3179b369ebc67d1bd7d16498b5e3131453f57e
Signed-off-by: Emma Foley <efoley@redhat.com>