[doc] Quota paramaters have moved to the [quota] section

This is a documentation bug.

With https://review.opendev.org/c/openstack/manila/+/799130
the quota configuration parameters:

    quota_shares
    quota_snapshots
    quota_gigabytes
    quota_per_share_gigabytes
    quota_snapshot_gigabytes
    quota_share_networks
    quota_share_replicas
    quota_replica_gigabytes
    quota_share_groups
    quota_share_group_snapshots
    quota_reservation_expire
    quota_until_refresh
    quota_max_age
    quota_driver

have moved to the [quota] section; and they have new names without the "quota_" prefix.

None of these parameters were previously documented in the administrator guide. A reference to this information exists in https://docs.openstack.org/manila/wallaby/admin/shared-file-systems-quotas.html

There is a reference to these options in the manually maintained configuration reference: https://docs.openstack.org/manila/wallaby/configuration/shared-file-systems/config-options.html#id6