bpo-40522: Replace PyThreadState_GET() with PyThreadState_Get() (GH-24575)

Use directly the PyThreadState_Get() function in public header files,
since PyThreadState_GET() macro is just an alias to it in pratice in
these files.
diff --git a/Include/cpython/object.h b/Include/cpython/object.h
index 86889f8..58e4d2b 100644
--- a/Include/cpython/object.h
+++ b/Include/cpython/object.h
@@ -528,7 +528,7 @@ PyAPI_FUNC(int) _PyTrash_cond(PyObject *op, destructor dealloc);
         /* If "cond" is false, then _tstate remains NULL and the deallocator \
          * is run normally without involving the trashcan */ \
         if (cond) { \
-            _tstate = PyThreadState_GET(); \
+            _tstate = PyThreadState_Get(); \
             if (_PyTrash_begin(_tstate, _PyObject_CAST(op))) { \
                 break; \
             } \