Update mypy settings

Author: AA-Turner

pyproject.toml

@@ -49,13 +49,13 @@ lint = [
     "ruff>=0.5",
     "mypy>=1.10",
     "types-docutils>=0.21",
+    "lxml-stubs>=0.4",
 ]
 test = [
     "pytest>=8.0",
     "pytest-deadfixtures>=2.2",
     "coverage>=6.5",
     "lxml>=4.9",
-    "lxml-stubs>=0.4",
     "setuptools>=70.0",  # for Cython compilation
     "typing_extensions>=4.9",  # for typing_extensions.Unpack
 ]
@@ -95,6 +95,10 @@ known_first_party = [ "sphinxarg", "test" ]
 line_length = 160
 multi_line_output = 3
 
+[tool.mypy]
+files = ["sphinxarg", "test"]
+python_version = "3.10"
+
 [[tool.mypy.overrides]]
 module = [
   "commonmark.*",