Update git submodules

Update git submodules

* Update docs/submodules/vid.git from branch 'master'
  to 6aa7736f462384347108732018f8a1dd3b4c4da8
  - Merge "Migrate vid docs"
  - Migrate vid docs

    Merging this will create
    https://onap-vid.readthedocs.io
    This build will run in parallel
    to the current docs generation method
    until we are ready to cut over.

    Issue-ID: CIMAN-364
    Signed-off-by: Jessica Wagantall <jwagantall@linuxfoundation.org>
    Change-Id: Iaa29f6ecfb1425464dc07fe396d2f8d0a3e72a85