Update git submodules

* Update openstack-ansible-os_neutron from branch 'master'
  - [ussuri][goal] Update contributor documentation
    
    This patch updates/adds the contributor documentation to follow
    the guidelines of the Ussuri cycle community goal[1].
    
    [1] https://governance.openstack.org/tc/goals/selected/ussuri/project-ptl-and-contrib-docs.html
    Story: #2007236
    Task: #38554
    
    Change-Id: If8017854d98fb0fc071d6afe23f6111da25aa8e4