Update git submodules

* Update docs/submodules/releng from branch 'master'
  - replace self-defined http codes with standard definitions

    Change-Id: I3045dc690e0bc1186f5c548cb533462dd03130d9
    Signed-off-by: SerenaFeng <feng.xiaowei@zte.com.cn>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 8d56e29..6f84a25 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 8d56e29f3dd1fad74a678202a70eb9d8bbf00bfc
+Subproject commit 6f84a256bbe92cf3f9f746ca0972abd9942bad43