Update deprecation logging doc with logger configuration (#47649)

Explicitly adds a configuration snippet to change logging level

docs/reference/setup/logging-config.asciidoc

@@ -211,7 +211,13 @@ logs to roll and compress after 1 GB, and to preserve a maximum of five log
 files (four rolled logs, and the active log).
 
 You can disable it in the `config/log4j2.properties` file by setting the deprecation
-log level to `error`.
+log level to `error` like this:
+[source,properties]
+--------------------------------------------------
+logger.deprecation.name = org.elasticsearch.deprecation
+logger.deprecation.level = error
+--------------------------------------------------
+
 
 You can identify what is triggering deprecated functionality if `X-Opaque-Id` was used as an HTTP header.
 The user ID is included in the `X-Opaque-ID` field in deprecation JSON logs.
@@ -265,4 +271,4 @@ appender.rolling.fileName = ${sys:es.logs.base_path}${sys:file.separator}${sys:e
 appender.rolling.layout.type = PatternLayout
 appender.rolling.layout.pattern = [%d{ISO8601}][%-5p][%-25c{1.}] [%node_name]%marker %.-10000m%n
 appender.rolling.filePattern = ${sys:es.logs.base_path}${sys:file.separator}${sys:es.logs.cluster_name}-%d{yyyy-MM-dd}-%i.log.gz
---------------------------------------------------
+--------------------------------------------------