tls: Disable a warning with LibreSSL >= 3.8.0
Skip a warning using EC_GFp_nist_method()
which was removed in LibreSSL 3.8.
Based on a patch from OpenBSD.
https://github.com/openbsd/ports/commit/33fe251a08cb11f30ce6094a2e0759c3bb63ed16
These functions are deprecated since OpenSSL 3.0.
https://www.openssl.org/docs/man3.1/man3/EC_GFp_nist_method.html