Update git submodules

* Update docs/submodules/releng from branch 'master'
  to 4e7d9403cf1371d4ab5fb1cd0467d06364433f61
  - Rather call python3

    IT fixes all deprecated python script calls.

    Change-Id: I5480c420b0963e717fab5835fcf17d435d111093
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 19b9c7a..4e7d940 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 19b9c7a165c39f186dbc52ef2e27083dbb1a63f1
+Subproject commit 4e7d9403cf1371d4ab5fb1cd0467d06364433f61