Update dependency oslo.db to v13 - wait for openstack-heat

The following discussion from !1934 (closed) should be addressed:

• @mrhopeman started a discussion:

  We need to wait for an update at openstack-heat to support newer oslo.db

from oslo.db commit 94d6e24ca1:

Remove sqlalchemy-migrate sqlalchemy-migrate does not support SQLAlchemy 2.x and we're not going to invest the time in changing this. Remove integration of sqlalchemy-migrate in oslo.db, allowing us to support SQLAlchemy 2.x fully.

Note that we do not remove the 'migration_cli' module entirely yet. While this is deprecated, it is possible to use this with alembic. New users shouldn't be switching to it, but any existing users can continue to use this module for some time yet.

Change-Id: Ic3d6bd318038d723b0d50d39e45f8e26289e9a57 Sem-Ver: api-break

So we need to wait for next oslo.db release and heat including that release.