Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Bumps OVS version to 2.8 for OVN

    OVS 2.7 does not seem to be available anymore in the copr repo and has
    been replaced by 2.8.

    Change-Id: I7ba98f14e9c9c34f6802f8a890876363c839ab9b
    Signed-off-by: Tim Rozet <trozet@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 6ea9c7c..807fad2 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 6ea9c7cca9b137f049362a27369edef43470b907
+Subproject commit 807fad268c90649f2901c5f5c4cdeb788a0308e0