doc/conf: work around __annotate_func__ sphinx autodoc errors on Python 3.14

On Python3.14, sphinx 8.2.3 stumbles upon __annotate_func__ members:

  WARNING: autodoc: failed to import 'UDisks2Device.__annotate_func__' from module 'labgrid.util.agents.udisks2'; the following exception was raised:
  Traceback (most recent call last):
    File "sphinx/sphinx/util/inspect.py", line 461, in safe_getattr
      return getattr(obj, name, *defargs)
  AttributeError: type object 'UDisks2Device' has no attribute '__annotate_func__'

This will be fixed once [1] is part of a release. Until then, exlcude the
member from autodoc.

[1] sphinx-doc/sphinx@7814844

Signed-off-by: Bastian Krause <bst@pengutronix.de>

Author: Bastian-Krause

doc/conf.py

@@ -175,8 +175,12 @@
 # -- Options for autodoc --------------------------------------------------
 
 autodoc_member_order = 'bysource'
+# TODO: __annotate_func__ can be dropped once
+# https://github.com/sphinx-doc/sphinx/commit/78148440556d3e5962771c1025c85b253ccd73c8
+# is part of a sphinx release
 autodoc_default_options = {
         'special-members': True,
+        'exclude-members': '__annotate_func__',
 }
 autodoc_mock_imports = ['onewire',
                         'gi',