hoon: remove +hint:ax

all this did was set .nut. while it could be used with doccords, it is
currently unused, and none of the other values in the sample of _ax are
set this way (bug, def, cox, hay, dom). i experimented a little bit with
trying to make use of this but it made things overall more unreadable,
and it wouldn't make sense to do it without doing the same for other
values of the sample. im guessing this is just an old style.

pkg/arvo/sys/hoon.hoon

@@ -7590,10 +7590,6 @@
       %bcwt  $(mod i.p.mod)
       %bczp  ~
     ==
-  ++  hint
-    |=  not=note
-    ^+  +>
-    ?>(?=(~ nut) +>.$(nut `not))
   ::
   ++  function
     ::  construct a function example