statem_clnt_construct_test.c: Use snprintf() instead of BIO_snprintf()

Fixes bfa50e13f85

Reviewed-by: Daniel Kubec <kubec@openssl.foundation>
Reviewed-by: Milan Broz <mbroz@openssl.org>
Merge-date: Mon Sep  7 14:48:56 2026
Merged-from: https://github.com/openssl/openssl/pull/32723