[hotfix] Fix the comment typo of TabletServerGateway (#740)

Author: majialoong

fluss-rpc/src/main/java/com/alibaba/fluss/rpc/gateway/TabletServerGateway.java

@@ -48,7 +48,7 @@
 
 import java.util.concurrent.CompletableFuture;
 
-/** The entry point of RPC gateway interface for coordinator server. */
+/** The entry point of RPC gateway interface for tablet server. */
 public interface TabletServerGateway extends RpcGateway, AdminReadOnlyGateway {
 
     /**