Issue #28858: Remove _PyObject_CallArg1() macro

Replace
   _PyObject_CallArg1(func, arg)
with
   PyObject_CallFunctionObjArgs(func, arg, NULL)

Using the _PyObject_CallArg1() macro increases the usage of the C stack, which
was unexpected and unwanted. PyObject_CallFunctionObjArgs() doesn't have this
issue.

Python/_warnings.c

@@ -476,7 +476,7 @@ warn_explicit(PyObject *category, PyObject *message,
     }
     else {
         text = message;
-        message = _PyObject_CallArg1(category, message);
+        message = PyObject_CallFunctionObjArgs(category, message, NULL);
         if (message == NULL)
             goto cleanup;
     }