Use const uint8_t[] instead of vectors for QUIC initial obfuscation salts This fixes a compilation error in chromium (and a style guide violation). gfe-relnote: refactor CryptoUtils::CreateInitialObfuscators, no behavior change (also gated behind quic_enable_version_50 or quic_supports_tls_handshake) PiperOrigin-RevId: 273848506 Change-Id: I06c247c5abeeef20d7fe88dee490c7b7a68bf81f