Revert "Add support for NAPI 6"

This reverts commit 6c83b0f.

Author: addaleax

include/ref-napi.h

@@ -1,9 +1,7 @@
 #ifndef REF_NAPI_H
 #define REF_NAPI_H
 
-#if !defined(NAPI_VERSION) || NAPI_VERSION < 6
 #include <get-symbol-from-current-process.h>
-#endif
 #include "napi.h"
 
 // The definitions in this file are intended to be used by node-ffi-napi.

src/binding.cc

@@ -24,7 +24,6 @@ using namespace Napi;
 
 namespace {
 
-#if !defined(NAPI_VERSION) || NAPI_VERSION < 6
 napi_status napix_set_instance_data(
     napi_env env, void* data, napi_finalize finalize_cb, void* finalize_hint) {
   typedef napi_status (*napi_set_instance_data_fn)(
@@ -51,17 +50,6 @@ napi_status napix_get_instance_data(
     return napi_generic_failure;
   return napi_get_instance_data__(env, data);
 }
-#else // NAPI_VERSION >= 6
-napi_status napix_set_instance_data(
-    napi_env env, void* data, napi_finalize finalize_cb, void* finalize_hint) {
-  return napi_set_instance_data(env, data, finalize_cb, finalize_hint);
-}
-
-napi_status napix_get_instance_data(
-    napi_env env, void** data) {
-  return napi_get_instance_data(env, data);
-}
-#endif
 
 // used by the Int64 functions to determine whether to return a Number
 // or String based on whether or not a Number will lose precision.