Simplify overflow handling code
Simplify overflow handling code

The code that is being removed is untested and does not seem to make
fixing an overflow any easier.  The fixer code just needs to know
which subtable caused the overflow and does not care about the item
within.  As such, no point in trying to find a "right" item.

In fact, leaving item as is, is more useful in debugging overflows
as it reflects which item's offset actually overflowed.

Part of fixing https://github.com/behdad/fonttools/issues/537

fonttools/fonttools,googlefonts/fonttools