Bump minimal puppet version to 6.0.0 in metadata.json

Author: Daniel Carabas

metadata.json

@@ -77,7 +77,7 @@
   "requirements": [
     {
       "name": "puppet",
-      "version_requirement": ">= 5.5.0 < 8.0.0"
+      "version_requirement": ">= 6.0.0 < 8.0.0"
     }
   ],
   "pdk-version": "1.19.0.pre (47)",