[#64033592] Remove ClamAV

We're now using the standard Ubuntu package.
[#64033592] Remove Solr

We are no longer using Solr. Long live Elasticsearch.
[#64033592] Remove Graphite

We are now using gds-operations/puppet-graphite which installs from pip into
a Python virtualenv.
Merge pull request #1 from alphagov/remove_unused_packages

[#64033592] Remove unused packages