Update git submodules

* Update docs/submodules/yardstick from branch 'stable/euphrates'
  - bugfix: tc023 miss description and tc050-58 wrong description

    also modify tc019,025,045-49 descrition to be unified

    JIRA: YARDSTICK-850

    Change-Id: I3f775f1ebff4063edc53b9bc26d7ba10b8af8a9d
    Signed-off-by: rexlee8776 <limingjiang@huawei.com>
    (cherry picked from commit 84a532cc7fbe2d99300d43b5431a7e3c5b2d22cc)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index f6aeffd..b553e72 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit f6aeffdfb89cd82d89dd8cd6d9e4711015a27d1d
+Subproject commit b553e726ac2d0aa3c62a510116e591392a104883