(maint) Use default heap size in travis tests
(maint) Use default heap size in travis tests

We are currently causing ENOMEM errors in our travis testing from
running Facter 2.x in our CI with JRuby 9k. We expect switching to using
Facter 3 when they implement java support for the gem to fix this issue.

Lowering the heap size should help with the memory consumption of the
forked processes that facter 2 creates. In local testing lowering the
heap caused negligible test run time differences.

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