Fix ruff deprecation warnings for top-level linter settings (#2430)

Author: correctmost

pyproject.toml

@@ -83,11 +83,13 @@ ignore_missing_imports = true
 
 
 [tool.ruff]
+target-version = "py38"
 
 # ruff is less lenient than pylint and does not make any exceptions
 # (for docstrings, strings and comments in particular).
 line-length = 110
 
+[tool.ruff.lint]
 select = [
     "E",  # pycodestyle
     "F",  # pyflakes
@@ -112,8 +114,7 @@ fixable = [
     "RUF", # ruff
 ]
 unfixable = ["RUF001"]
-target-version = "py38"
 
-[tool.ruff.per-file-ignores]
+[tool.ruff.lint.per-file-ignores]
 # Ruff is autofixing a tests with a voluntarily sneaky unicode
 "tests/test_regrtest.py" = ["RUF001"]