Fix invalid isort configuration in setup.cfg

Author: althonos

setup.cfg

@@ -99,10 +99,12 @@ per-file-ignores =
     fs/_pathcompat.py:C401
 
 [isort]
-default_section = THIRD_PARTY
+default_section = THIRDPARTY
 known_first_party = fs
 known_standard_library = typing
 line_length = 88
+profile = black
+skip_gitignore = true
 
 # --- Test and coverage configuration ------------------------------------------