Clarify the "refresh_inventory" meta task when using a dynamic inventory script (#37575)

Clarify the "refresh_inventory" meta task when using a dynamic inventory script since it was somehow documented in this old mailing list message:
https://groups.google.com/forum/#!topic/ansible-project/ImhePKKDBZM

lib/ansible/modules/utilities/helper/meta.py

@@ -31,7 +31,9 @@ options:
           points to implicitly trigger handler runs (after pre/post tasks, the final role execution, and the main tasks section of your plays).
         - >
           C(refresh_inventory) (added in 2.0) forces the reload of the inventory, which in the case of dynamic inventory scripts means they will be
-          re-executed. This is mainly useful when additional hosts are created and users wish to use them instead of using the `add_host` module."
+          re-executed. If the dynamic inventory script is using a cache, Ansible cannot know this and has no way of refreshing it (you can disable the cache
+          or, if available for your specific inventory datasource (for es.: aws), you can use the an inventory plugin instead of an inventory script).
+          This is mainly useful when additional hosts are created and users wish to use them instead of using the `add_host` module."
         - "C(noop) (added in 2.0) This literally does 'nothing'. It is mainly used internally and not recommended for general use."
         - "C(clear_facts) (added in 2.1) causes the gathered facts for the hosts specified in the play's list of hosts to be cleared, including the fact cache."
         - "C(clear_host_errors) (added in 2.1) clears the failed state (if any) from hosts specified in the play's list of hosts."