src: remove TLSEXT_TYPE_alpn guard

TLSEXT_TYPE_application_layer_protocol_negotiation is always defined in
all supported OpenSSL versions. We also use this macro elsewhere without
guards, so if it did not exist, compilation would have already failed.

Besides that, it makes little sense to provide a TLS 1.3 implementation
that does not support ALPN.

PR-URL: #46956
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Filip Skokan <panva.ip@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

src/node_constants.cc

@@ -1032,10 +1032,8 @@ void DefineCryptoConstants(Local<Object> target) {
     NODE_DEFINE_CONSTANT(target, DH_NOT_SUITABLE_GENERATOR);
 #endif
 
-#ifdef TLSEXT_TYPE_application_layer_protocol_negotiation
 #define ALPN_ENABLED 1
     NODE_DEFINE_CONSTANT(target, ALPN_ENABLED);
-#endif
 
 #ifdef RSA_PKCS1_PADDING
     NODE_DEFINE_CONSTANT(target, RSA_PKCS1_PADDING);