Update robot comments documentation to reflect current behaviour

Robot comments are currently displayed in the web UI, despite
from what the documentation says.

Change-Id: I9e57b25f94001dc8ee123086c2a46fd89330dd1d
diff --git a/Documentation/config-robot-comments.txt b/Documentation/config-robot-comments.txt
index 0077697..f5185a4 100644
--- a/Documentation/config-robot-comments.txt
+++ b/Documentation/config-robot-comments.txt
@@ -36,7 +36,6 @@
 
 == Limitations
 
-* Robot comments are not displayed in the web UI yet.
 * There is no support for draft robot comments, but robot comments are
   always published and visible to everyone who can see the change.