Update set_fact doc to reflect updated caching options (#46565)

* Update set_fact doc to reflect updated caching options

* add note about change in precedence caused by caching

lib/ansible/modules/utilities/logic/set_fact.py

@@ -21,8 +21,9 @@ module: set_fact
 short_description: Set host facts from a task
 description:
     - This module allows setting new variables.  Variables are set on a host-by-host basis just like facts discovered by the setup module.
-    - These variables will be available to subsequent plays during an ansible-playbook run, but will not be saved across executions even if you use
-      a fact cache.
+    - These variables will be available to subsequent plays during an ansible-playbook run.
+    - Set C(cacheable) to C(yes) to save variables across executions
+      using a fact cache. Variables created with set_fact have different precedence depending on whether they are or are not cached.
     - Per the standard Ansible variable precedence rules, many other types of variables have a higher priority, so this value may be overridden.
       See L(Variable Precedence Guide,../user_guide/playbooks_variables.html#variable-precedence-where-should-i-put-a-variable) for more information.
     - This module is also supported for Windows targets.