Fix this error:

[polynomia] updating environment: [new config] 62 added, 0 changed, 0 removed
[polynomia] Extension error (sage.docs.conf):
[polynomia] Handler <function find_sage_dangling_links at 0x7f92ac43f520> for event 'missing-reference' threw an exception (exception: No such config value: intersphinx_disabled_reftypes)

diff -up src/sage/docs/conf.py.orig src/sage/docs/conf.py
--- src/sage/docs/conf.py.orig	2022-03-04 16:33:15.479009340 -0700
+++ src/sage/docs/conf.py	2022-03-06 18:49:34.742628130 -0700
@@ -910,6 +910,7 @@ def setup(app):
     if app.srcdir.startswith(SAGE_DOC_SRC):
         app.add_config_value('intersphinx_mapping', {}, False)
         app.add_config_value('intersphinx_cache_limit', 5, False)
+        app.add_config_value('intersphinx_disabled_reftypes', [], False)
         app.connect('config-inited', set_intersphinx_mappings)
         app.connect('builder-inited', intersphinx.load_mappings)
         # We do *not* fully initialize intersphinx since we call it by hand