demos/bio/sconnect.c: Free ssl_bio on error to avoid memory leak

demos/bio/sconnect.c: Free ssl_bio on error to avoid memory leak

Call BIO_free() to release ssl_bio if an error occurs before BIO_push(), preventing a memory leak.

Fixes: 396e720965 ("Fix certificate validation for IPv6 literals in sconnect demo")
Signed-off-by: JiashengJiang <jiasheng@purdue.edu>
Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/27639)