Revert "Merge branch 'pr/2801'"

This reverts commit ea304a00efd5aa5837ab74979b60a1597d4eb82d, reversing
changes made to b9a0cb902a8a77635d1c0fba99a5a4ebad8197c1.
(PUP-2828) Select the branch of puppet-win32-ruby to install

Previously, we were always installing ruby 1.9.3 on Windows, which
contains the gem sets for 3.2.x to 3.6.x.

This commit updates the setup step to install ruby from the 1.9.3-x86
branch (by default). If the WIN32_RUBY_ARCH environment variable is
specified, then it will install ruby from the 2.0.0-x64 branch instead.
Merge branch 'master' of https://github.com/puppetlabs/puppet