Update git submodules

* Update docs/submodules/apex from branch 'stable/danube'
  - Disable tripleo_ui

    Change-Id: Ib35bc67d15c306b416801838bba48b7090bff174
    Signed-off-by: Feng Pan <fpan@redhat.com>
    (cherry picked from commit bf3e6ff5f6a46f1b0bc9d44f27a305aa4f26c469)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index d5a8930..1ed4b47 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit d5a893088b4965806ae81dbc08ba2bf9da23a72e
+Subproject commit 1ed4b476cc7569b63567b73badaee578b3ed8fc5