update puppet-systemd upper bound to 8.0.0

Author: TheMeier

metadata.json

@@ -115,7 +115,7 @@
     },
     {
       "name": "puppet/systemd",
-      "version_requirement": ">= 6.3.0 < 7.0.0"
+      "version_requirement": ">= 6.3.0 < 8.0.0"
     }
   ]
 }