Clarify MQTT docs when logging is disabled

Related to esphome/issues#6046,
it isn't necissary to remove the api component entirely.

In fact, it is kinda nice to keep it there for tailing logs if the
log_topic is `null`.

This clarifies that you can just set `reboot_timeout` and keep it
enabled.

components/mqtt.rst

@@ -12,8 +12,8 @@ in which case this is not needed.
 
 .. warning::
 
-    If you enable MQTT and you do *not* use the "native API" for Home Assistant, you must
-    remove the ``api:`` line from your ESPHome configuration, otherwise the ESP will
+    If you enable MQTT and you do *not* use the :doc:`/components/api`, you must
+    remove the ``api:`` configuration or set ``reboot_timeout: 0s``, otherwise the ESP will
     reboot every 15 minutes because no client connected to the native API.
 
 .. code-block:: yaml