[8.x] fix intersphinx cache

doc/usage/extensions/intersphinx.rst

@@ -126,28 +126,6 @@ linking:
                   ('../../otherbook/build/html/objects.inv', None)),
       }
 
-   **Old format for this config value**
-
-   .. deprecated:: 6.2
-
-   .. RemovedInSphinx80Warning
-
-   .. caution:: This is the format used before Sphinx 1.0.
-                It is deprecated and will be removed in Sphinx 8.0.
-
-   A dictionary mapping URIs to either ``None`` or an URI.  The keys are the
-   base URI of the foreign Sphinx documentation sets and can be local paths or
-   HTTP URIs.  The values indicate where the inventory file can be found: they
-   can be ``None`` (at the same location as the base URI) or another local or
-   HTTP URI.
-
-   Example:
-
-   .. code:: python
-
-      intersphinx_mapping = {'https://docs.python.org/': None}
-
-
 .. confval:: intersphinx_cache_limit
 
    The maximum number of days to cache remote inventories.  The default is