Update git submodules

* Update docs/submodules/apex from branch 'stable/euphrates'
  - Increase memory size for virt-customize

    Some of the bigger commands can exceed the default,
    so increase all instances for consistency. It's
    unlikely build machines won't have 4G of memory
    available.

    Change-Id: Ifa575b6e6faef9ba038900ab0e080da15d5680aa
    JIRA: APEX-520
    Signed-off-by: Michael Chapman <michapma@redhat.com>
    (cherry picked from commit 0220094bfe4abdc964f282f4f01190897e3065e4)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 7771d50..189b69a 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 7771d5010b9845576ceb0bbe5ad5f405ed99b871
+Subproject commit 189b69a875d3eefca2a7eb3fa354b9f4930cbcd7