chore(deps): Update outdated GitHub Actions versions (#34544)

This PR updates an outdated GitHub Action version.

- Updated `astral-sh/setup-uv` from `v6` to `v7` in
`.github/actions/uv_setup/action.yml`

Looks like this was missed as part of
https://github.com/langchain-ai/langchain/pull/33457 so hopefully safe
to bring it into alignment.