Update pypy documentation with corrected links (#1114)

Author: oscargus

docs/pypy.rst

@@ -11,13 +11,13 @@ PyPy 7.3.10 and newer versions are supported, though with some limitations:
 
 1. When nanobind types occur in reference cycles, then those cycles are not
    collectable and will be leaked. This is a limitation of PyPy's ``cpyext``
-   layer that was reported in `PyPy issue #3849
-   <https://foss.heptapod.net/pypy/pypy/-/issues/3849>`_. Note that this would
+   layer that was reported in `PyPy issue #3848
+   <https://github.com/pypy/pypy/issues/3848>`_. Note that this would
    only affects users that use the :cpp:class:`nb::type_slots() <type_slots>`
    feature to implement a custom ``Py_tp_traverse`` or ``Py_tp_clear`` slot.
 
 2. nanobind normally complains about any reference leaks involving instances,
    functions, and types when the interpreter shuts down. PyPy lacks the final
    garbage collection step that is needed to identify such leaks See `PyPy
-   issue #3855 <https://foss.heptapod.net/pypy/pypy/-/issues/3855>`_. Those
-   those checks therefore had to be disabled when compiling for PyPy.
+   issue #3855 <https://github.com/pypy/pypy/issues/3855>`_. Those
+   checks therefore had to be disabled when compiling for PyPy.