gst/typefind/gsttypefindfunctions.c: Remove part from previous commit that was bogus: g_utf8_validate() does in fact ...

Original commit message from CVS:
* gst/typefind/gsttypefindfunctions.c:
(utf8_type_find_have_valid_utf8_at_offset):
Remove part from previous commit that was bogus:
g_utf8_validate() does in fact not accept embedded
zeroes, so we don't need to check for those (thanks
to Mike for the hint).