Use cron_core v1.2.0 to fix an error

Error message (using 1.0.0):
error during compilation: Parameter minute failed on Cron[puppet_agent_every_thirty]:
Munging failed for value 23 in class minute: undefined method `=~' for 23:Integer
(file: ./puppet-module-puppet/spec/fixtures/modules/puppet/manifests/init.pp, line: 62)

Author: Phil Friderici

.fixtures.yml

@@ -2,7 +2,7 @@ fixtures:
   repositories:
     cron:
       repo: 'https://github.com/puppetlabs/puppetlabs-cron_core.git'
-      ref: '1.0.0'
+      ref: 'v1.2.0'
     inifile:
       repo: 'https://github.com/puppetlabs/puppetlabs-inifile.git'
       ref: '1.6.0'