This removes the request spec online data migration
routine added via change I61b9b50436d8bdb8ff06259cc2f876502d688b91
in Newton.
A nova-status upgrade check was added for this in Rocky with
change I1fb63765f0b0e8f35d6a66dccf9d12cc20e9c661 so operators should
be able to tell, either from the results of the nova-status upgrade
check command or "nova-manage db online_data_migrations" command,
whether or not they have completed the migration and can upgrade to
Stein.
This also allows us to start removing the various compat checks
in the API and conductor services for old instances that predated
having a request spec since those should have a request spec now
via the online data migration.
Related to blueprint request-spec-use-by-compute
Change-Id: Ib0de49b3c0d6b3d807c4eb321976848773c1a9e8
ed4fe3ead6