metadata: stick to puppetlabs-concat 1.x

The puppetlabs-concat 2.x series has been yanked. Since we don't know what
format the new module will take, we should not declare compatibility with it.

See https://groups.google.com/forum/#!topic/puppet-users/4_Sxrfl4uUY

Reverts 4fd696f

metadata.json

@@ -10,7 +10,7 @@
   "dependencies": [
     {"name":"puppetlabs/stdlib","version_requirement":">= 4.2.0 <5.0.0"},
     {"name":"puppetlabs/apt","version_requirement":">= 1.8.0 <3.0.0"},
-    {"name":"puppetlabs/concat","version_requirement":">= 1.1.1 <3.0.0"}
+    {"name":"puppetlabs/concat","version_requirement":">= 1.1.1 <2.0.0"}
   ],
   "requirements": [
     {