Mistake in usage drop_constraint parameters

[Ann Taraday]

In miration e197124d4b9_add_unique_constrain mistake in usage drop_constraint parameter type_ and positional agruments name
and table_name.

File "/opt/stack/neutron/neutron/db/migration/alembic_migrations/versions/e197124d4b9_add_unique_constrain.py", line 64, in downgrade
    type='unique'
TypeError: drop_constraint() takes at least 2 arguments (1 given)

The same mistake was already fixed in miration 63afba73813_ovs_tunnelendpoints_id_unique.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/59910

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/59910
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=51ef6a1dc30576f31a8a120066d81feedd0bf224
Submitter: Jenkins
Branch: master

commit 51ef6a1dc30576f31a8a120066d81feedd0bf224
Author: Ann Kamyshnikova <email address hidden>
Date: Wed Dec 4 10:59:59 2013 +0400

    Fix mistake in usage drop_constraint parameters

    In migration e197124d4b9_add_unique_constrain mistake in usage
    drop_constraint parameter type_ and positional arguments name
    and table_name.

    The same mistake was already fixed in migration
    63afba73813_ovs_tunnelendpoints_id_unique.

    Change-Id: I6a250e55ea53048bb11afd71fecf94da6f0c7421
    Closes-bug: #1257607