simplify flux restful

[vsoch]

remove the flux multi-user auth, there is only one way to interact with flux restful and create users that seems to reliably work. I need to still update docs and update the testing (which will likely fail now)

TODO:

• update docs (for secretKey) and multi-user example here
• bump and deploy fluxoperator python sdk here
• update flux-cloud docs, finish google cloud example
• figure out filter for jobs (maybe make user queues?) Future improvements - multiple job query and job labeling flux-restful-api#49