Bump Python version of `ci-tpu-test-trigger` to 3.12. (#9665)
`ci-tpu-test-trigger` was failing with:
```
Downloading https://us-python.pkg.dev/ml-oss-artifacts-published/jax/meson-python/meson_python-0.18.0-py3-none-any.whl
...
meson-python: error: The package requires Python version >=3.11, running on 3.10.18
```
