remove deprecation of facter --puppet

Help for facter --puppet states {{Deprecated: use 'puppet facts' instead)}

Except FACT-96 was updated in 2015 with:

We reversed course on the deprecation, at least until puppet facts offers full parity.

puppet facts does not include many facter options (like, but not limited to --no-custom-facts) valuable for debugging, and some users avoid deprecated functionality in principle or policy.

(The Release notes for Facter 3.0 that mentions facter -p has been restored have since aged out of our document tree, because 2015 < 2019.)