include/openssl/asn1.h: Remove version dependent inclusion of <openssl/bn.h>
It's unclear if this dependency was because ASN1 functions that use
BIGNUM didn't exist before 1.1.0, or if it was a mistaken attempt at
deprecation. Since there exist ASN1 functions using BIGNUM now, it
seems pointless to keep that check, and unnecessarily including
<openssl/bn.h> should be harmless either way.
Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10364)