Remove documentation for method ins since it no longer exists

Author: Jan-Olof Hendig

doc/Type/IO/Handle.pod

@@ -130,12 +130,6 @@ offset if you want to position before the end of the file.
 
 Return the current position of the file pointer in bytes.
 
-=head2 method ins
-
-    method ins(IO::Handle:D: --> Int)
-
-Return the number of lines read from the file.
-
 =head2 method slurp-rest
 
     multi method slurp-rest(IO::Handle:D: :$bin! --> Buf)