Removed ASN1_STRING_data()

Removed ASN1_STRING_data()

This has been deprecated since 1.1.0 and is in the way for
improvements that could make ASN1_STRING opaque. (#29177)

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Norbert Pocs <norbertp@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/29149)