Revert "Changed our acceptance test setup to pin on facter 2.1.0"

This reverts commit 72a1588fd5019de9c9801974b9ef4c25625dcc48.

The tests should now use puppetlabs/puppetdb 4.0.0. The 4.0.0 module
depends on puppetlabs/postgresql 4.0.0, which has a fix for the facter
issue, so we no longer need to pin on an older facter.
Merge pull request #1084 from senior/maint/stable/revert-facter-pinning

(PDB-873) Revert "Changed our acceptance test setup to pin on facter 2.1.0"