bpo-41078: Rename pycore_tupleobject.h to pycore_tuple.h (GH-21056)

diff --git a/Modules/_functoolsmodule.c b/Modules/_functoolsmodule.c
index f1ee23f..8120140 100644
--- a/Modules/_functoolsmodule.c
+++ b/Modules/_functoolsmodule.c
@@ -1,6 +1,6 @@
 #include "Python.h"
 #include "pycore_pystate.h"       // _PyThreadState_GET()
-#include "pycore_tupleobject.h"
+#include "pycore_tuple.h"         // _PyTuple_ITEMS()
 #include "structmember.h"         // PyMemberDef
 
 /* _functools module written and maintained