[docs] fix invalid TODO comment (#3452)

diff --git a/src/core/thread/mesh_forwarder_ftd.cpp b/src/core/thread/mesh_forwarder_ftd.cpp
index e2bba2e..c5331bc 100644
--- a/src/core/thread/mesh_forwarder_ftd.cpp
+++ b/src/core/thread/mesh_forwarder_ftd.cpp
@@ -846,7 +846,7 @@
 #endif
         else
         {
-            // TODO: support ALOC for Commissioner, Neighbor Discovery Agent
+            // TODO: support for Neighbor Discovery Agent ALOC
             ExitNow(error = OT_ERROR_DROP);
         }
     }