Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Merge "Removes clean.sh"
  - Removes clean.sh

    CI has been migrated to use opnfv-clean for verify jobs, which is now
    installed as python.  There is no reason to keep ci/clean.sh anymore.

    Change-Id: I2edf23901c5debaba0674e3506fd0392d317dc6f
    Signed-off-by: Tim Rozet <trozet@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 2784827..23acd48 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 2784827b0d2e3e2f904964c89db2421d4ababebd
+Subproject commit 23acd4820209eef14ee9001646ecb81856ce18b2