bpo-42519: Replace PyObject_MALLOC() with PyObject_Malloc() (GH-23587)

No longer use deprecated aliases to functions:

* Replace PyObject_MALLOC() with PyObject_Malloc()
* Replace PyObject_REALLOC() with PyObject_Realloc()
* Replace PyObject_FREE() with PyObject_Free()
* Replace PyObject_Del() with PyObject_Free()
* Replace PyObject_DEL() with PyObject_Free()
diff --git a/Objects/complexobject.c b/Objects/complexobject.c
index a481d9a..a65ebdf 100644
--- a/Objects/complexobject.c
+++ b/Objects/complexobject.c
@@ -233,7 +233,7 @@ PyObject *
 PyComplex_FromCComplex(Py_complex cval)
 {
     /* Inline PyObject_New */
-    PyComplexObject *op = PyObject_MALLOC(sizeof(PyComplexObject));
+    PyComplexObject *op = PyObject_Malloc(sizeof(PyComplexObject));
     if (op == NULL) {
         return PyErr_NoMemory();
     }