`orbax-checkpoint` broken on Windows since 0.11.33

I wanted to try on Flax for size, but am unfortunately hoping to run it on a Windows system.

Since Flax depends on `orbax-export`, which in turn depends on `orbax-checkpoint`, this no longer works on Windows due to the recently added dependency `uvloop` (see: https://github.com/google/orbax/commit/ebffb79bb1ec3a20cd336b9c23f8529b383f8a42) , which is Unix-only. There is a fork that also supports Windows (Winloop).

## Reproducer (on Windows):
```sh
uv pip install orbax-checkpoint
Resolved 22 packages in 276ms
× Failed to build `uvloop==0.22.1`
├─▶ The build backend returned an error
╰─▶ Call to `setuptools.build_meta.build_wheel` failed (exit code: 1)

[stderr]
Traceback (most recent call last):
File "", line 14, in
requires = get_requires_for_build({})
File "C:\Users\jeppe\AppData\Local\uv\cache\builds-v0\.tmpXe8j9j\Lib\site-packages\setuptools\build_meta.py", line 333, in
get_requires_for_build_wheel
return self._get_build_requires(config_settings, requirements=[])
~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\jeppe\AppData\Local\uv\cache\builds-v0\.tmpXe8j9j\Lib\site-packages\setuptools\build_meta.py", line 301, in
_get_build_requires
self.run_setup()
~~~~~~~~~~~~~~^^
File "C:\Users\jeppe\AppData\Local\uv\cache\builds-v0\.tmpXe8j9j\Lib\site-packages\setuptools\build_meta.py", line 317, in run_setup
exec(code, locals())
~~~~^^^^^^^^^^^^^^^^
File "", line 8, in
import setuptools.build_meta as backend
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: uvloop does not support Windows at the moment

hint: This usually indicates a problem with the package or the build environment.
help: `uvloop` (v0.22.1) was included because `orbax-checkpoint` (v0.11.33) depends on `uvloop`
```

## Workaround:

Installing or pinning to `orbax-checkpoint<=0.11.32`