Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "add pep8 check task for doctor"
  - add pep8 check task for doctor

    Change-Id: Ibd595748910b143ae3e9373bccf4b4e6b54dd931
    Signed-off-by: dongwenjuan <dong.wenjuan@zte.com.cn>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index bd62919..b6d433b 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit bd629199ec422bc8d89823c44e158cd53bb5d532
+Subproject commit b6d433bf86cc2eeea568b5b9b52f30b8826baed3