Make apt-update depend on the right repo (DataDog#610)

It shouldn't change much, but this is the right thing to do.

Author: albertvaka

manifests/ubuntu.pp

@@ -73,7 +73,7 @@
 
   package { $datadog_agent::params::package_name:
     ensure  => $platform_agent_version,
-    require => [Apt::Source['datadog6'],
+    require => [Apt::Source['datadog'],
                 Class['apt::update']],
   }