Update nova-manage doc page
Update nova-manage doc page

nova-manage doc page [1] mentioned usage of `nova-manage db archive`
command, which doesn't exist.

This change updates the doc page with the correct command
`nova-manage db archive_deleted_rows`.

[1] https://docs.openstack.org/nova/latest/cli/nova-manage.html

Closes-Bug: #1981088
Change-Id: Ibcbccf87ec70e9edea61c99d4d3bcf610cc1df64

mahak/nova,openstack/nova,mahak/nova,openstack/nova,mahak/nova,openstack/nova