Change joda style pattern to java style (#15695) (#15711)

since 7.0 elasticsearch is using java.time style patterns.
YYYY becomes yyyy

Co-authored-by: Przemyslaw Gomulka <[email protected]>

Author: ycombinator

libbeat/docs/shared-ilm.asciidoc

@@ -66,7 +66,7 @@ Date math is supported in this setting. For example:
 
 [source,yaml]
 ----
-setup.ilm.pattern: "{now/M{YYYY.MM}}-000001"
+setup.ilm.pattern: "{now/M{yyyy.MM}}-000001"
 ----
 
 For more information, see