tox/sphinx-dev: s/allowlist_externals/whitelist_externals/

tox.ini

@@ -17,7 +17,7 @@ commands =
   {envpython} -m pifpaf run postgresql -- make -C docs {posargs:html}
 
 [testenv:sphinx-dev]
-allowlist_externals = make
+whitelist_externals = make
 # workaround really long dependencies installation due to the
 # new pip resolver and its backtracking processes
 install_command = make pip-install-swh-dev {packages}