Drop mentions of previously removed black and isort (#1180)

Author: asvetlov

requirements/lint.txt

@@ -1,6 +1,4 @@
 -r ci.txt
 -r towncrier.txt
 
-black==25.1.0
-isort==6.0.1
 pre-commit==4.2.0

setup.cfg

@@ -46,13 +46,3 @@ install_requires =
   typing-extensions >= 4.1.0; python_version < '3.11'
 packages =
   multidict
-
-
-[isort]
-multi_line_output=3
-include_trailing_comma=True
-force_grid_wrap=0
-use_parentheses=True
-
-known_first_party=multidict
-known_third_party=pytest