(maint) Pin puppet git acceptance to use facter 2.0.2

Previously, when running acceptance tests on platforms that still use
git checkouts, e.g. Windows, we were installing puppet#stable and
facter#stable. However, we recently released facter 2.1, which now
resides in facter#stable. On Windows, facter 2.1 requires a newer
win32-security gem than what puppet#stable installs, causing errors
like:

lib/win32/security.rb:54:in `elevated_security?': Incorrect function

This commit ensures we install facter 2.0.2 (commit 7845c9aa0df) when
running acceptance from git checkouts. This should only affect Windows
and Solaris, as Linux acceptance runs against packages, which will pull
in the most recently released dependencies.