[io grant] Remove mention of role IO

Still need to move all the routines documented in IO.pod6
to appropriate files before nixing IO.pod6 file altogether. For now,
at least remove the mention that role IO is a thing.

Author: zoffixznet

doc/Type/IO.pod6

@@ -2,12 +2,7 @@
 
 =TITLE role IO
 
-=SUBTITLE Input/output related object
-
-    role IO { }
-
-The IO role provides no functionality itself; it simply marks that a
-particular object relates to input/output.
+=SUBTITLE Input/output related routines
 
 Please note that coercion via L<Cool.IO|/type/Cool#method_IO> leads to
 L<IO::Path|/type/IO::Path>. This is the exception from the rule.