mrd: remove redundant validation in HTTP endpoint (#8685)
mrd: remove redundant validation in HTTP endpoint (#8685)

The `regionForJob` function in the HTTP job endpoint overrides the region for
multiregion jobs to `global`, which is used as a sentinel value in the
server's job endpoint to avoid re-registration loops. This changeset removes
an extraneous check that results in errors in the web UI and makes
round-tripping through the HTTP API cumbersome for all consumers.
burdandrei/nomad,hashicorp/nomad,hashicorp/nomad,hashicorp/nomad,dvusboy/nomad,dvusboy/nomad,dvusboy/nomad,hashicorp/nomad,burdandrei/nomad,hashicorp/nomad,dvusboy/nomad,dvusboy/nomad,dvusboy/nomad,hashicorp/nomad,dvusboy/nomad,burdandrei/nomad,burdandrei/nomad,burdandrei/nomad,burdandrei/nomad,burdandrei/nomad