Use _PyDict_NewPresized() in _PyStack_AsDict()

Issue #27810.
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 351c6eb..67b163d 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -2378,7 +2378,7 @@
     PyObject *kwdict;
     Py_ssize_t i;
 
-    kwdict = PyDict_New();
+    kwdict = _PyDict_NewPresized(nkwargs);
     if (kwdict == NULL) {
         return NULL;
     }