Remove several unused TypeVars (#6829)

stdlib/imp.pyi

@@ -1,7 +1,7 @@
 import types
 from _typeshed import StrPath
 from os import PathLike
-from typing import IO, Any, Protocol, TypeVar
+from typing import IO, Any, Protocol
 
 from _imp import (
     acquire_lock as acquire_lock,
@@ -15,8 +15,6 @@ from _imp import (
     release_lock as release_lock,
 )
 
-_T = TypeVar("_T")
-
 SEARCH_ERROR: int
 PY_SOURCE: int
 PY_COMPILED: int