Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 9c5d989770e4d35c5645fe4c4f7f0d0bcd12210b
  - nit: remove append option

    Change-Id: Ib0427bed2e85f1d20067b710afddb77d1dcf0e2b
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 4e1cbe8..9c5d989 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 4e1cbe883d795b50a11b9ea5cea932e06e663c55
+Subproject commit 9c5d989770e4d35c5645fe4c4f7f0d0bcd12210b