Remove usage of load_documentation_profile in docs

With aiida-core/pull/6226 the usage of load_documentation_profile is not
anymore required as the Django backend is not anymore supported and can
therefore be removed.

docs/source/conf.py

@@ -14,16 +14,8 @@
 import sys
 import time
 
-from aiida.manage.configuration import load_documentation_profile
-
 import aiida_restapi
 
-# -- AiiDA-related setup --------------------------------------------------
-
-# Load the dummy profile even if we are running locally, this way the documentation will succeed even if the current
-# default profile of the AiiDA installation does not use a Django backend.
-load_documentation_profile()
-
 extensions = [
     'myst_parser',
     'sphinx_external_toc',