Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Merge "Change destination of snmp mibs files from /usr/share/mibs/ietf to /usr/share/snmp/mibs, and create symbolic link from ietf to snmp/mibs."
  - Change destination of snmp mibs files from
    /usr/share/mibs/ietf to /usr/share/snmp/mibs,
    and create symbolic link from ietf to snmp/mibs.

    Change-Id: Icf3ff3659f63222cc3a5e8f1f93fe183a2b86f45
    Signed-off-by: jhinman1 <john.hinman@intel.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index c6f04a5..974e251 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit c6f04a5dee991a131a49c2fde9c5990fe2edac4e
+Subproject commit 974e251a7c6461805443e35f78e21a8bfe88a67b