Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge changes from topics 'testapi', 'yamllint'

    * changes:
      delete legacy update code
      fix yamllint verify fail

  - delete legacy update code

    update directory was employed to update TestAPI before auto deployment
    is adopted, now it is useless and can be deleted.

    Change-Id: I4e5ae84e80879cd9f711dc1d02224ae4f5902e49
    Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>
  - fix yamllint verify fail

    fail record: https://build.opnfv.org/ci/job/opnfv-yamllint-verify-master/1050/console

    Change-Id: Ic709b9a3d1d3642a3deebd930714a2ba2de22da6
    Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>