Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "[yardstick] update yardstick email list"
  - [yardstick] update yardstick email list

    remove Ross as he is no longer PTL.

    Change-Id: I2661cf09cae4be5c16d06a237d2dbe1c7c591cfc
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 9705226..51a7113 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 9705226e4b6f530508697a2206a758a522b5e97b
+Subproject commit 51a7113c8e7be8b2287641dea7a8a227fc02daa2