Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Apex: Do not use apex branch in promote gs path

    When we promote artifacts we do not want to include the apex branch (for
    example "gambia") in the gs path URL for where snapshots are uploaded.
    We may use a different apex branch to promote older OS versions of
    snapshots, but we still want a unified url of just
    apex/<os_version>/<topology> for our snapshot artifacts.

    Change-Id: I7dfe40558ce05d04e1805884cd6a47c82220581e
    Signed-off-by: Tim Rozet <trozet@redhat.com>