Cleanup quality (#21493)

* Remove mentions of flake8/isort

* Clean up inits

* Deall with all other inits

* Last special rule for dummy files

pyproject.toml

@@ -8,6 +8,12 @@ ignore = ["E501", "E741", "W605"]
 select = ["E", "F", "I", "W"]
 line-length = 119
 
+# Ignore import violations in all `__init__.py` files.
+[tool.ruff.per-file-ignores]
+"__init__.py" = ["E402", "F401", "F403", "F811"]
+"src/transformers/file_utils.py" = ["F401"]
+"src/transformers/utils/dummy_*.py" = ["F401"]
+
 [tool.ruff.isort]
 lines-after-imports = 2
 known-first-party = ["transformers"]