Update git submodules

* Update docs/submodules/releng from branch 'master'
  to afb1aa9ba453b4ab3873d1eb1fc533dc53f6ab18
  - Remove useless util jobs

    It must be noted that lf-build6 has been offline
    for a while.

    Change-Id: Ia3d7020975a199c0c4c00b13d3af9d719faad604
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index bff8119..afb1aa9 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit bff8119cdf465d38ec05a8310847117f713bd159
+Subproject commit afb1aa9ba453b4ab3873d1eb1fc533dc53f6ab18