Use the correct parameters for role assignements list

Since [1], keystone requires, for the role assignements index API call,
only the parameters defined in ``role_assignments_index_request_query``.

[1]https://review.opendev.org/c/openstack/keystone/+/940344

Change-Id: I67e7f81b460e9517fc77d96bc4f35ef9300dbf74
diff --git a/octavia_tempest_plugin/tests/test_base.py b/octavia_tempest_plugin/tests/test_base.py
index 7f4ae3e..f176cb1 100644
--- a/octavia_tempest_plugin/tests/test_base.py
+++ b/octavia_tempest_plugin/tests/test_base.py
@@ -211,7 +211,7 @@
                 user_name = cred
                 cred_obj = getattr(cls, 'os_' + cred)
             params = {'user.id': cred_obj.credentials.user_id,
-                      'project.id': cred_obj.credentials.project_id}
+                      'scope.project.id': cred_obj.credentials.project_id}
             roles = cls.os_admin.role_assignments_client.list_role_assignments(
                 **params)['role_assignments']
             for role in roles: