Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Migrates from queens to rocky

    For now we need to retain the ability to deploy odl-queens for CSIT.

    Change-Id: Idea550ff5e7aeb230aa93d3575de11e5e9656302
    Signed-off-by: Tim Rozet <trozet@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index ee58a24..df388a8 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit ee58a24647df8eec2418735b038e5035bdffe10d
+Subproject commit df388a8afedc29f9cfebdab3cc39ef27f93d9612