pythongh-135965: Delete duplicate word in isolating-extensions howto (python#135964)

Change use use to use.

Author: LamentXU123

Doc/howto/isolating-extensions.rst

@@ -453,7 +453,7 @@ Avoiding ``PyObject_New``
 
 GC-tracked objects need to be allocated using GC-aware functions.
 
-If you use use :c:func:`PyObject_New` or :c:func:`PyObject_NewVar`:
+If you use :c:func:`PyObject_New` or :c:func:`PyObject_NewVar`:
 
 - Get and call type's :c:member:`~PyTypeObject.tp_alloc` slot, if possible.
   That is, replace ``TYPE *o = PyObject_New(TYPE, typeobj)`` with::