QUIC: removed compatibility with older BoringSSL API. SSL_CIPHER_get_protocol_id() appeared in BoringSSL somewhere between BORINGSSL_API_VERSION 12 and 13 for compatibility with OpenSSL 1.1.1. It was adopted without a proper macro test, which remained unnoticed. This justifies that such old BoringSSL API isn't widely used and its support can be dropped. While here, removed SSL_set_quic_use_legacy_codepoint() that became useless after the default was flipped in BoringSSL over a year ago.