[3.14] Link to 3.14 GC design docs (python#139387)

Author: hauntsaninja

Doc/library/gc.rst

@@ -140,7 +140,7 @@ The :mod:`gc` module provides the following functions:
 
    *threshold2* is ignored.
 
-   See `Garbage collector design <https://devguide.python.org/garbage_collector>`_ for more information.
+   See `Garbage collector design <https://github.com/python/cpython/blob/3.14/InternalDocs/garbage_collector.md>`_ for more information.
 
    .. versionchanged:: 3.14
       *threshold2* is ignored