HBASE-26738 Correct description of WAL directory in doc (#4097)

Signed-off-by: Duo Zhang <zhangduo@apache.org>

Author: ryantotti

src/main/asciidoc/_chapters/architecture.adoc

@@ -1180,7 +1180,7 @@ In 0.94, HLog was the name of the implementation of the WAL.
 You will likely find references to the HLog in documentation tailored to these older versions.
 ====
 
-The WAL resides in HDFS in the _/hbase/WALs/_ directory, with subdirectories per region.
+The WAL resides in HDFS in the _/hbase/WALs/_ directory, with subdirectories per RegionServer.
 
 For more general information about the concept of write ahead logs, see the Wikipedia
 link:http://en.wikipedia.org/wiki/Write-ahead_logging[Write-Ahead Log] article.