[io grant] Remove mention of IO.umask

Author: zoffixznet

doc/Language/5to6-perlfunc.pod6

@@ -1634,12 +1634,6 @@ Works as a function and a method. C<uc("ha")> and C<"ha".uc> both return "HA".
 Perl 6 has done away with C<ucfirst>. The title case function L<C<tc>|/routine/tc> probably
 does what you need.
 
-=head2 umask
-
-=item umask EXPR
-
-Is an C<IO> method. C<IO.umask> returns the umask.
-
 =head2 undef
 
 =item undef EXPR