Upgrade pytest configuration (#1189)

Use the new proper TOML support [added in pytest
9](https://docs.pytest.org/en/stable/changelog.html#pytest-9-0-0-2025-11-05).

Author: adamchainz

pyproject.toml

@@ -59,7 +59,7 @@ test = [
   "mariadb-dyncol",
   "mysqlclient>=1.4.3",
   "parameterized",
-  "pytest",
+  "pytest>=9",
   "pytest-django",
   "pytest-flake8-path",
   "pytest-randomly",
@@ -147,13 +147,9 @@ warn_unused_ignores = true
 overrides = [ { module = "tests.*", allow_untyped_defs = true } ]
 
 [tool.pytest]
-ini_options.addopts = """\
-    --strict-config
-    --strict-markers
-    --ds=tests.settings
-    """
-ini_options.django_find_project = false
-ini_options.xfail_strict = true
+strict = true
+django_find_project = false
+DJANGO_SETTINGS_MODULE = "tests.settings"
 
 [tool.coverage]
 run.branch = true