Update git submodules

Update git submodules

* Update docs/submodules/apex from branch 'stable/gambia'
  - Gambia Branch Configuration for Docs and Gitreview

    Update the docs to use 'Gambia' as the version and release, and sets the
    default gitreview branch to 'stable/gambia' so it doesn't need to be
    explicly passed every time.

    Change-Id: Id5cbfb581cb232af5541f58df8c95e4b0918713e
    Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>
  - Fixes undercloud accidentally using wrong images/containers

    Our undercloud initial install was failing with queens because the
    --use-heat arg does not work the same way as master/rocky. Therefore the
    undercloud install would fail, and then try to reinstall on the next
    ansible task. This one would succeed, via container installation because
    we were using the wrong undercloud/overcloud disk images.

    Change-Id: Ifb829aeeec991ba6dbe582fda3e9ee6b9bc733df
    Signed-off-by: Tim Rozet <trozet@redhat.com>
  - Local Documentation Builds

    This adds configuration for performing local documentation builds
    with the following simple command:

    tox -e docs

    This patch is part of our documentation effor to Move away from submodules
    https://docs.opnfv.org/en/latest/how-to-use-docs/local-build-transition.html

    added index.rst so that docs build succsesfully

    Change-Id: I2d28f03ad4d5c9c14de095dc544257af9d1e51d9
    Signed-off-by: Aric Gardner <agardner@linuxfoundation.org>
    (cherry picked from commit 9666d8bb3df726d88d08d5811d2a99e713908396)

  - Migrates deploy settings for Gambia

    With branching to gambia we need to move the settings back to their
    proper names and remove OpenStack branch as Queens is the default for
    Gambia.

    Change-Id: Ia6101289629d89fa349f6554436ccd7c0f8b3c0c
    Signed-off-by: Tim Rozet <trozet@redhat.com>
  - Enable OVN scenarios

    As of Queens only HA OVN deployments are supported.

    Change-Id: I184c5a096fec9cbc3cf2ec06218700138ea3ed57
    Signed-off-by: Tim Rozet <trozet@redhat.com>
    (cherry picked from commit ee58a24647df8eec2418735b038e5035bdffe10d)