[skip ci] Add comment for milvus.yaml (#12608)

Signed-off-by: NBennu <yunmei.li@zilliz.com>

configs/milvus.yaml

@@ -46,7 +46,7 @@ rocksmq:
   path: /var/lib/milvus/rdb_data # The path where the message is stored in rocksmq
   rocksmqPageSize: 2147483648 # 2 GB, 2 * 1024 * 1024 * 1024 bytes
   retentionTimeInMinutes: 10080 # 7 days, 7 * 24 * 60 minutes, The retention time of the message in rocksmq.
-  retentionSizeInMB: 8192 # 8 GB, 8 * 1024 MB
+  retentionSizeInMB: 8192 # 8 GB, 8 * 1024 MB, The retention size of the message in rocksmq.
 
 # Related configuration of rootCoord, used to handle data definition language (DDL) and data control language (DCL) requests
 rootCoord: