ldns_dane_match_any_cert_with_data: fix types

ldns_dane_match_any_cert_with_data: fix types

Both `i` and `n` should match the return type for `sk_X509_num` (which
is `int`, not `size_t`). This addresses a potential issue where
`sk_X509_num(..)` could return -1, resulting in an unnecessary number of
loop iterations and undesirable behavior.

Reported by:	Coverity
Signed-off-by: Enji Cooper <yaneurabeya@gmail.com>