(maint) Remove branches from travis
(maint) Remove branches from travis

To reduce maintenance costs and ensure that all new branches are tested,
here I remove the branches from the .travis.yml file.

puppetlabs/puppet-server,puppetlabs/puppet-server,puppetlabs/puppetserver,puppetlabs/puppetserver,puppetlabs/puppetserver,puppetlabs/puppet-server,puppetlabs/puppetserver