Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Apex: fix unbound variable in artifact dl

    We still need VERSION_EXTENSION var to figure out which RPM files to
    remove on the slave.

    Change-Id: I03cc9c3318edec9860c8f3ffc01db52517a644b4
    Signed-off-by: Tim Rozet <trozet@redhat.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 10ed113..cde4c43 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 10ed113d9e0581a9e9b5afddd1a3b924e6b81e2d
+Subproject commit cde4c43d8694ae2182c0200bac6f3e3fd535bec6