Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Add API(v2) to delete certain project"
  - Add API(v2) to delete certain project

    JIRA: YARDSTICK-734

    API: /api/v2/yardstick/projects/<project_id>
    METHOD: DELETE

    Change-Id: I6628ec42aa7c4c6ab073ddc33c119ea1c03b81fe
    Signed-off-by: chenjiankun <chenjiankun1@huawei.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index bc750fb..f8e0986 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit bc750fbee81d0b3a9edbd16c88c02e785f87dd7f
+Subproject commit f8e09865fe1fb8fe26bb7b686db96b72e8b480ef