Update git submodules

Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 219801fef20c8cd1838328bd6a3c557092754a7c
  - Merge "Support CentOS 7 in GoogleStorage Gitlab template"
  - Support CentOS 7 in GoogleStorage Gitlab template

    Add a check for `dnf` to the GoogleStorage gitlab-ci template, falling
    back to `yum` if the command is not available. This should allow the job
    to work on both CentOS 7 and 8.

    Change-Id: I0964c23d799bb394bc331bd740a0d6a1cba74082
    Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>