Update git submodules

* Update docs/submodules/qtip from branch 'master'
  - Merge "Delete part of code under qtip/legacy"
  - Delete part of code under qtip/legacy

    These code is obsolete.

    Change-Id: I0fc2b12847aaa30f713cf7578a92aae912153dd6
    Signed-off-by: zhihui wu <wu.zhihui1@zte.com.cn>

diff --git a/docs/submodules/qtip b/docs/submodules/qtip
index 8d1912b..31937f7 160000 (submodule)
--- a/docs/submodules/qtip
+++ b/docs/submodules/qtip
@@ -1 +1 @@
-Subproject commit 8d1912b86d0a31954abdad05198bb2d69e51e8c7
+Subproject commit 31937f72f6fd0f44d26da673127cded6cc217975