Update git submodules

* Update docs/submodules/yardstick from branch 'stable/danube'
  - Bugfix: fix typo

    Change-Id: I9b7cd5f94b1663af3b807ce24c941868b10d85d1
    Signed-off-by: JingLu5 <lvjing5@huawei.com>
    (cherry picked from commit a84dfcb92e1de313fea7841224be5a374a2d2184)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 7f445a3..87d8de2 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 7f445a38e9bc572cce0c7616a24480e7c7b31109
+Subproject commit 87d8de27074f71db307891e1230a9341f852d945