HBASE-25862 update reference guide for log4j2.xml (#3252)

src/main/asciidoc/_chapters/configuration.adoc

@@ -636,7 +636,9 @@ read by HBase daemons on startup.
 Changes here will require a cluster restart for HBase to notice the change.
 
 [[log4j]]
-=== _log4j.properties_
+=== _log4j2.xml_
+
+Since version 3.0.0, HBase has upgraded to Log4j2, so the configuration file name and format has changed. Read more in link:https://logging.apache.org/log4j/2.x/index.html[Apache Log4j2].
 
 Edit this file to change rate at which HBase files are rolled and to change the level at which
 HBase logs messages.