Update git submodules

* Update docs/submodules/integration.git from branch 'master'
  to 688355bf09c08f3a54362efe36eb7da0f3f09ca2
  - Fix missing images in staging manifest

    In order to unblock other teams, revert missing images in the
    staging manifest to their respective casablanca release
    versions.

    Change-Id: I37fa7791649d184bda3fac3178944e8c1e53d798
    Issue-ID: SDC-2114
    Issue-ID: MULTICLOUD-475
    Signed-off-by: Gary Wu <gary.i.wu@huawei.com>

diff --git a/docs/submodules/integration.git b/docs/submodules/integration.git
index 942aae2..688355b 160000 (submodule)
--- a/docs/submodules/integration.git
+++ b/docs/submodules/integration.git
@@ -1 +1 @@
-Subproject commit 942aae25af859316017e5de9c0a95db28208a88c
+Subproject commit 688355bf09c08f3a54362efe36eb7da0f3f09ca2