tests(fixtures) rename gitconfig param to vcs_gitconfig

why: libvcs 0.41.0 renamed the pytest plugin's `gitconfig` fixture
to `vcs_gitconfig`. vcspull's three call sites must update to the
new parameter name or pytest fixture resolution fails at collection.
what:
- conftest.py:setup() — request `vcs_gitconfig` instead of `gitconfig`
- tests/test_fixtures.py — update test_home_contains_gitconfig and
  the embedded conftest text in test_pytester_git_commit_in_isolated_run

Author: tony

conftest.py

@@ -38,7 +38,7 @@ def add_doctest_fixtures(
 def setup(
     request: pytest.FixtureRequest,
     monkeypatch: pytest.MonkeyPatch,
-    gitconfig: pathlib.Path,
+    vcs_gitconfig: pathlib.Path,
     set_home: pathlib.Path,
     xdg_config_path: pathlib.Path,
     git_commit_envvars: dict[str, str],

tests/test_fixtures.py

@@ -37,7 +37,7 @@ def test_git_commit_envvars_in_environment(
 
 def test_home_contains_gitconfig(
     set_home: pathlib.Path,
-    gitconfig: pathlib.Path,
+    vcs_gitconfig: pathlib.Path,
 ) -> None:
     """HOME should point to a directory containing .gitconfig."""
     home = os.environ.get("HOME", "")
@@ -136,7 +136,7 @@ def test_pytester_git_commit_in_isolated_run(
 def setup(
     request: pytest.FixtureRequest,
     monkeypatch: pytest.MonkeyPatch,
-    gitconfig: pathlib.Path,
+    vcs_gitconfig: pathlib.Path,
     set_home: pathlib.Path,
     git_commit_envvars: dict[str, str],
 ) -> None: