Fix minimum version requirement for stdlib

Since c0b8640, we use the namespaced
version of `stdlib::ensure_packages`, which appeared in version 9.0.0 of
the stdlib module.

Adjust the version requirement accordingly.

Author: smortex

metadata.json

@@ -10,7 +10,7 @@
   "dependencies": [
     {
       "name": "puppetlabs/stdlib",
-      "version_requirement": ">= 4.16.0 < 10.0.0"
+      "version_requirement": ">= 9.0.0 < 10.0.0"
     }
   ],
   "operatingsystem_support": [