Replace deprecated tox.ini option (#762)

This option was replaced in 2020, deprecated, and eventually removed in
tox 4. The correct option already appears elseware in this tox.ini file.

This fix is necessary to run `tox -e doc` per the README.md
instructions on tox 4.

Signed-off-by: Eric Searcy <[email protected]>
Co-authored-by: Elena Kolevska <[email protected]>

Author: emsearcy

tox.ini

@@ -88,7 +88,7 @@ commands_pre =
 [testenv:doc]
 basepython = python3
 usedevelop = False
-whitelist_externals = make
+allowlist_externals = make
 deps = sphinx
 commands =
     sphinx-apidoc -E -o docs/actor dapr/actor