reworded copy option docs to be clearer

library/files/unarchive

@@ -39,7 +39,8 @@ options:
     default: null
   copy:
     description:
-      - Should the file be copied from the local to the remote machine?
+      - If set to yes/true (default), the file is copied from the 'master' to the target machine,
+      if set to no/false, the plugin will look for src archive at the target machine.
     required: false
     choices: [ "yes", "no" ]
     default: "yes"