[CI] Use older commit for puppet-catalog-test

After `puppet-catalog-test` has been recently updated it failed
in our CI with:

     File[/etc/apt/sources.list] has notify relationship to invalid
     resource Exec[apt_updated]

See #8814 for more details.

Resolves: #8814

https://github.com/invadersmustdie/puppet-catalog-test/commit/ac386793c2c456d2071dd0adda716224128f0bb3

tests/platform-ci/Gemfile

@@ -12,6 +12,6 @@ group :test do
   gem "mocha"
   # Use puppet-catalog-test from git because last released gem 0.4.2 gives a deprecation
   # warning: "[DEPRECATION] `last_comment` is deprecated.  Please use `last_description` instead."
-  gem "puppet-catalog-test", :git => 'https://github.com/invadersmustdie/puppet-catalog-test.git'
+  gem "puppet-catalog-test", :git => 'https://github.com/invadersmustdie/puppet-catalog-test.git', :ref => 'ac386793c2c456d2071dd0adda716224128f0bb3'
   gem "leap_cli", :git => 'https://leap.se/git/leap_cli.git'
 end