Remove left over code for filter_validation

This extension in neutron-lib was released in 1.18.0 so it is time to
use the extension from neutron-lib.

Change-Id: I992b37fed0cf4898a730f19e49690050017ec0a7
Related-Bug: #1749820

neutron/extensions/_filter_validation_lib.py

@@ -1,30 +0,0 @@
-#    Licensed under the Apache License, Version 2.0 (the "License"); you may
-#    not use this file except in compliance with the License. You may obtain
-#    a copy of the License at
-#
-#         http://www.apache.org/licenses/LICENSE-2.0
-#
-#    Unless required by applicable law or agreed to in writing, software
-#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
-#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
-#    License for the specific language governing permissions and limitations
-#    under the License.
-
-"""
-This module should be deleted once neutron-lib containing
-https://review.opendev.org/#/c/580190/ change is released.
-"""
-
-
-ALIAS = 'filter-validation'
-IS_SHIM_EXTENSION = True
-IS_STANDARD_ATTR_EXTENSION = False
-NAME = 'Filter parameters validation'
-DESCRIPTION = 'Provides validation on filter parameters.'
-UPDATED_TIMESTAMP = '2018-03-21T10:00:00-00:00'
-RESOURCE_ATTRIBUTE_MAP = {}
-SUB_RESOURCE_ATTRIBUTE_MAP = {}
-ACTION_MAP = {}
-REQUIRED_EXTENSIONS = []
-OPTIONAL_EXTENSIONS = []
-ACTION_STATUS = {}

neutron/extensions/filter_validation.py

@@ -16,7 +16,7 @@ from neutron_lib.api import extensions
 from oslo_config import cfg
 from oslo_log import log as logging
 
-from neutron.extensions import _filter_validation_lib as apidef
+from neutron_lib.api.definitions import filter_validation as apidef
 
 
 LOG = logging.getLogger(__name__)