MAINT: Don't wrap #include <Python.h> with extern "C"

This extern block was recently moved, which exposed a latent bug in CPython
(python/cpython#127772), but it's probably not a
good practice in general to wrap other code's headers with extern
guards.

Author: hawkinsp

numpy/_core/include/numpy/ndarraytypes.h

@@ -1,15 +1,15 @@
 #ifndef NUMPY_CORE_INCLUDE_NUMPY_NDARRAYTYPES_H_
 #define NUMPY_CORE_INCLUDE_NUMPY_NDARRAYTYPES_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include "npy_common.h"
 #include "npy_endian.h"
 #include "npy_cpu.h"
 #include "utils.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define NPY_NO_EXPORT NPY_VISIBILITY_HIDDEN
 
 /* Always allow threading unless it was explicitly disabled at build time */