Update git submodules

* Update docs/submodules/yardstick from branch 'stable/danube'
  - Adding Labels

    Labels serve as anchors/ refs when referenced from other documents
    This patch adds labels to docs/*/*/index.rst

    Change-Id: I046277771130cc6298636fb30f9d6dae7de224cf
    Signed-off-by: rexlee8776 <limingjiang@huawei.com>
    (cherry picked from commit 6509a1b7ce0cd16f17ea3116af25794938c93566)

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 06c0f07..b2a7981 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 06c0f074a136414d1e9704aa4e30c62e50f2d5ce
+Subproject commit b2a79813f57a94b6565fa8f967d10d295010dfff