Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "Add GERRIT_REFSPEC to 'project-parameter' Macro"
  - Add GERRIT_REFSPEC to 'project-parameter' Macro

    GERRIT_REFSPEC is always passed by the gerrit-trigger plugin when a job
    is triggered by Gerrit. Because it is not explicily defined, there is no
    way to manually trigger jobs, as the git clone looks up the list of refs
    by GERRIT_REFSPEC.

    Being able to manually trigger jobs (with node parameters so they can be
    restricted) is very helpful in debugging CI issues.

    Change-Id: I8a1d9ea380902fc95f30482e5acb616347709ab1
    Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index da95fe6..4b1560c 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit da95fe6416a07fde7619002395ed0ec5a956ce02
+Subproject commit 4b1560c6499e53efb3b2ca83294265052396b2d5