Merge pull request #9713 from bcoca/fact_cache_n_gathering

mentioned gathering settings in fact caching.

docsite/rst/playbooks_variables.rst

@@ -795,6 +795,8 @@ To configure fact caching, enable it in ansible.cfg as follows::
     fact_caching_timeout = 86400
     # seconds
 
+You might also want to change the 'gathering' setting to 'smart' or 'explicit' or set gather_facts to False in most plays.
+
 At the time of writing, Redis is the only supported fact caching engine.
 To get redis up and running, perform the equivalent OS commands::