bpo-29464: Rename METH_FASTCALL to METH_FASTCALL|METH_KEYWORDS and make (#1955)

the bare METH_FASTCALL be used for functions with positional-only
parameters.
diff --git a/Modules/clinic/_weakref.c.h b/Modules/clinic/_weakref.c.h
index 139a0e1..97e2a24 100644
--- a/Modules/clinic/_weakref.c.h
+++ b/Modules/clinic/_weakref.c.h
@@ -44,16 +44,12 @@
                                    PyObject *key);
 
 static PyObject *
-_weakref__remove_dead_weakref(PyObject *module, PyObject **args, Py_ssize_t nargs, PyObject *kwnames)
+_weakref__remove_dead_weakref(PyObject *module, PyObject **args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     PyObject *dct;
     PyObject *key;
 
-    if (!_PyArg_NoStackKeywords("_remove_dead_weakref", kwnames)) {
-        goto exit;
-    }
-
     if (!_PyArg_ParseStack(args, nargs, "O!O:_remove_dead_weakref",
         &PyDict_Type, &dct, &key)) {
         goto exit;
@@ -63,4 +59,4 @@
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=05ecbb46c85839a2 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=87ddb70850080222 input=a9049054013a1b77]*/