Update git submodules

* Update docs/submodules/apex from branch 'stable/danube'
  - Pins ODL L3 VPP/HC packages

    JIRA: APEX-421

    Change-Id: I18a1624af96be772820938e3138666c51b10301c
    Signed-off-by: Tim Rozet <trozet@redhat.com>
    (cherry picked from commit 621bfd97aa74877177039ada39c0c8f9578a0220)

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 8d22b80..1a667b0 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 8d22b800fe8d26748abc35f59c034936624a29b3
+Subproject commit 1a667b0f76e3c281946d22a8a8b951498be23872