Add TODO around removing black in the future

Author: JohnGarbutt

tox.ini

@@ -25,6 +25,8 @@ commands =
     ruff check {tox_root} --fix
 
 [testenv:black]
+# TODO: understand why ruff doesn't fix
+# line lenghts as well as black does
 commands = black {tox_root} --check
 
 [testenv:codespell]