Update checks running on `RPSaaSDev` and their `required` status.

Per my conversation with @rkmanda


Also need to update relevant doc on ARM wiki:

> Per https://aka.ms/azsdk/api-versions the RPSaaSDev branch has no checks running on it, but
> [the ARM wiki](https://armwiki.azurewebsites.net/rpaas/swaggeronboarding.html) says:
>
> > No formal PR review process is required to merge in RPSaaSDev, but must pass basic validations (syntactic and semantic) to ensure openapi spec is valid. You'll also need an approval from a member of your team who is part of the [RP Platform Users group](https://armwiki.azurewebsites.net/rpaas/swaggeronboarding.html#prerequisites).

This is loosely related to https://github.com/Azure/azure-sdk-tools/issues/6374

@weshaggard FYI