build: fix windows build

Be very careful with forward declarations, MSVC is quite picky and
rather stupid about it.

Fixes #5810.

src/node_buffer.cc

@@ -21,7 +21,6 @@
 
 
 #include "node.h"
-#include "node_internals.h"
 #include "node_buffer.h"
 #include "smalloc.h"
 #include "string_bytes.h"