Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 6bbe8a9bb459a381f31db46cd2257652cb6a109b
  - Create stable branch for docs

    stable/jerma for opnfvdocs

    Signed-off-by: Sofia Wallin <sofia.wallin@est.tech>
    Change-Id: If74dee858d212f67cf2add7b84834e33c7ce6949

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 40a430f..6bbe8a9 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 40a430f39052b4b3fd167d610747a9406a2a7bd6
+Subproject commit 6bbe8a9bb459a381f31db46cd2257652cb6a109b