Revert "fixup! pytester: typing for spawn/spawn_pytest"

This reverts commit 4022ef0.

Author: blueyed

src/_pytest/pytester.py

@@ -18,11 +18,6 @@
 from typing import Optional
 from typing import Sequence
 from typing import Tuple
-
-try:
-    from typing import TYPE_CHECKING
-except ImportError:
-    from typing_extensions import TYPE_CHECKING
 from typing import Union
 from weakref import WeakKeyDictionary
 
@@ -40,7 +35,7 @@
 from _pytest.pathlib import Path
 from _pytest.reports import TestReport
 
-if TYPE_CHECKING:
+if False:  # TYPE_CHECKING
     from typing import Type
 
     import pexpect