HDFS-17279. RBF: Fix link to Fedbalance document (#6333). Contributed by Haiyang Hu.

Reviewed-by: Inigo Goiri <inigoiri@apache.org>
Signed-off-by: Ayush Saxena <ayushsaxena@apache.org>

hadoop-hdfs-project/hadoop-hdfs-rbf/src/site/markdown/HDFSRouterFederation.md

@@ -539,7 +539,7 @@ More metrics info can see [RBF Metrics](../../hadoop-project-dist/hadoop-common/
 Router Federation Rename
 -------
 
-Enable Router to rename across namespaces. Currently it is implemented based on [HDFS Federation Balance](../../hadoop-federation-balance/HDFSFederationBalance.md) and has some limits comparing with normal rename.
+Enable Router to rename across namespaces. Currently it is implemented based on [HDFS Federation Balance](../../hadoop-federation-balance/HDFSFederationBalance.html) and has some limits comparing with normal rename.
 1. It is much slower than the normal rename so need a longer RPC timeout configuration. See `ipc.client.rpc-timeout.ms` and its description for more information about RPC timeout.
 2. It doesn't support snapshot path.
 3. It doesn't support to rename path with multiple destinations.