[DOCS] Update default value of index.name.time_format (elastic#56453)

Corrects the default value of index.name.time_format

Author: jaijhala

docs/reference/settings/monitoring-settings.asciidoc

@@ -244,7 +244,7 @@ anything defined here.
 `index.name.time_format`::
 
 A mechanism for changing the default date suffix for the, by default, daily Monitoring indices.
-The default value is `YYYY.MM.DD`, which is why the indices are created daily.
+The default value is `yyyy.MM.dd`, which is why the indices are created daily.
 
 `use_ingest`::