refactor: restore typing for non-backports

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

cibuildwheel/_compat/typing.py

@@ -1,9 +1,6 @@
 from __future__ import annotations
 
-import os
-import subprocess
 import sys
-from typing import TYPE_CHECKING, Union
 
 if sys.version_info < (3, 8):
     from typing_extensions import Final, Literal, OrderedDict, Protocol, TypedDict
@@ -18,33 +15,10 @@ else:
 __all__ = (
     "Final",
     "Literal",
-    "PLATFORMS",
-    "PathOrStr",
-    "PlatformName",
     "Protocol",
-    "PLATFORMS",
-    "PopenBytes",
     "Protocol",
     "TypedDict",
     "OrderedDict",
     "assert_never",
     "NotRequired",
 )
-
-
-if TYPE_CHECKING:
-    PopenBytes = subprocess.Popen[bytes]
-    PathOrStr = Union[str, os.PathLike[str]]
-else:
-    PopenBytes = subprocess.Popen
-    PathOrStr = Union[str, "os.PathLike[str]"]
-
-
-PlatformName = Literal["linux", "macos", "windows"]
-PLATFORMS: Final[set[PlatformName]] = {"linux", "macos", "windows"}
-
-
-class GenericPythonConfiguration(Protocol):
-    @property
-    def identifier(self) -> str:
-        ...