Remove puppet 7 support (#18)

Author: gibbs

metadata.json

@@ -62,7 +62,7 @@
   "requirements": [
     {
       "name": "puppet",
-      "version_requirement": ">= 7.0.0 < 9.0.0"
+      "version_requirement": ">= 8.0.0 < 9.0.0"
     }
   ],
   "pdk-version": "3.4.0",