Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 7a300e64dddc158c6941e6bfd3b6fa66233a7561
  - Drop OPNFV arm64 support

    Armband left OPNFV.
    Functest still supports arm and arm64 via .travis-ci.

    Change-Id: Ie0c7de20182fa91231760ad29c3b38c8ca8c9779
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 16efea2..7a300e6 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 16efea266ab609265a2e84a351ad1178f13aa690
+Subproject commit 7a300e64dddc158c6941e6bfd3b6fa66233a7561