chore: use if TYPE_CHECKING: blocks (#2866)

unit_test/projectfiles_test.py

@@ -1,5 +1,6 @@
+from __future__ import annotations
+
 import tomllib
-from pathlib import Path
 from textwrap import dedent
 
 import pytest
@@ -10,6 +11,10 @@ from cibuildwheel.projectfiles import (
     setup_py_python_requires,
 )
 
+TYPE_CHECKING = False
+if TYPE_CHECKING:
+    from pathlib import Path
+
 
 def test_read_setup_py_simple(tmp_path: Path) -> None:
     with open(tmp_path / "setup.py", "w") as f: