sql: Remove dead code
sql: Remove dead code

Change I41584c652ab34a267009136ee2a2e159ee2f2a6e ("sql: Squash mitaka
migrations") removed the final users of the 'get_constraints_names',
'add_constraints' and 'remove_constraints' functions.

Change I96cab42cfcfd3e86b53f25abf4cf4043af3b5667 ("sql: Squash ocata
migrations") removed the final use of the 'USE_TRIGGERS' constant.

Change I59882d88fe593ec1ae37415b2157584f7f3c85f8 ("sql: Remove legacy
'migrate_repo' migration repo") removed the final use of
'_assert_not_schema_downgrade' function.

Change-Id: I8aa811ea336e9f613300bc21125e7582010cf5a5
Signed-off-by: Stephen Finucane <4725dc7f3632bf126d9fbdc30c347e91e8d2fe16@redhat.com>

mahak/keystone,openstack/keystone,mahak/keystone,openstack/keystone,mahak/keystone,openstack/keystone