docs: FuncADL Query Type documentation links to reference not using current API

[matthewfeickert]

As noted in iris-hep/analysis-systems-deliverables#1 (comment), the existing ServiceX client docs for FuncADL Query Type give @gordonwatts's https://github.com/gordonwatts/xaod_usage Jupyter Book as the full user docs reference.

ServiceX_frontend/docs/query_types.rst

Line 142 in 53226cd

Full documentation on the func-adl query language can be found at this `JupyterBook <https://gordonwatts.github.io/xaod_usage/intro.html>`_.

However, that Jupyter Book isn't using the v3.0.x API, so this will be important to update. While these are docs outside of this repository, they should still be kept up to date. It isn't reasonable to ask @gordonwatts to be the sole maintainer of that, so it would be great if the other members of the ServiceX development team (who have the API flow through their fingers at the moment while some of us are still kickstarting it a bit) could help update this.