gh-138098: Clarify strong references in PyDict_Next docs for free-threaded build

Doc/c-api/dict.rst

@@ -258,6 +258,17 @@ Dictionary Objects
    value represents offsets within the internal dictionary structure, and
    since the structure is sparse, the offsets are not consecutive.
 
+   .. note::
+
+      On the free-threaded build, this function can be used safely inside a
+      critical section. However, the references returned for *pkey* and *pvalue*
+      are :term:`borrowed <borrowed reference>` and are only valid while the
+      critical section is held. If you need to use these objects outside the
+      critical section or when the critical section can be suspended, create a
+      :term:`strong reference <strong reference>` (for example, using
+      :c:func:`Py_NewRef`).
+
+
    For example::
 
       PyObject *key, *value;
@@ -297,7 +308,7 @@ Dictionary Objects
 
       Py_BEGIN_CRITICAL_SECTION(self->dict);
       while (PyDict_Next(self->dict, &pos, &key, &value)) {
-          ...
+         ...
       }
       Py_END_CRITICAL_SECTION();