Update git submodules

* Update docs/submodules/apex from branch 'master'
  - More doc updates for Danube

    Change-Id: I125548acde034d8c4c85cce93fb001ba06c8ab33
    Signed-off-by: Tim Rozet <trozet@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 2852914..1d65553 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 28529146f87e5b725616c6574e69697410975f77
+Subproject commit 1d655538cfe9a665c5e12dc8b910ddaaae21bae7