Update git submodules

* Update docs/submodules/qtip from branch 'stable/danube'
  - Merge "Rename docs/testing/developer/design to docs/testing/developer/devguide" into stable/danube
  - Rename docs/testing/developer/design to docs/testing/developer/devguide

    See https://git.opnfv.org/opnfvdocs/tree/docs/testing/testing-dev.rst

    Change-Id: Iac14adf4a2876fd74972dcf6279f7022e92cb9b5
    Signed-off-by: Yujun Zhang <zhang.yujunz@zte.com.cn>

diff --git a/docs/submodules/qtip b/docs/submodules/qtip
index 19f370a..784ef9f 160000 (submodule)
--- a/docs/submodules/qtip
+++ b/docs/submodules/qtip
@@ -1 +1 @@
-Subproject commit 19f370a198baabed7a6bca3a149049bbc0f9ac73
+Subproject commit 784ef9f52c634aaa4e8727bb4a80cef1793d3391