Remove pip_lock_down dependency

The pip_install and pip_lock_down roles have been merged.

Remove pip_lock_down from the role's meta dependencies and test
requirements.

Change-Id: I1a62d627ee0f8c636065734e8d69fcfd009542a2

meta/main.yml

@@ -18,9 +18,8 @@ galaxy_info:
   - python
   - magnum
 dependencies:
+  - pip_install
   - role: apt_package_pinning
     when:
       - ansible_pkg_mgr == 'apt'
   - galera_client
-  - role: pip_install
-    pip_lock_to_internal_repo: "{{ not keystone_developer_mode | bool }}"

tests/ansible-role-requirements.yml

@@ -10,7 +10,3 @@
   src: https://git.openstack.org/openstack/openstack-ansible-pip_install
   scm: git
   version: master
-- name: pip_lock_down
-  src: https://git.openstack.org/openstack/openstack-ansible-pip_lock_down
-  scm: git
-  version: master