doc: update planned features

I think statistics are good at this point and timeouts do not sound like
a good idea to me any more: What are we going to do when a timeout is
hit?

src/vmod_slash.vcc

@@ -1215,8 +1215,6 @@ FELLOW PLANNED BUT MISSING FEATURES
 
 The following features are planned for implementation:
 
-* More Statistics
-* I/O Timeouts
 * Support some successor of xkey (additional cache keys)
 * Further improve cache loading speed