[DRE-maint] Bug#808348: Please remove ancient Chef 10 server packages

[Aaron Stone]

Package: chef-server-api

The chef-server-api package should be removed, since Chef 10 is no
longer supported upstream and Chef 11 and higher now use Erchef
(Erlang Chef) on the server side.

The following rather ancient Chef 10 server packages should be removed
please: chef-server-api, chef-server-webui, chef-solr, chef-expander

Once these are gone, we can also remove the ancient Ruby Merb packages
in #794904 as these Chef packages should be the last dependencies on
Merb.