Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Remove network_services.vnf_generic.vnf.prox_helpers.ProxSocketHelper.rx_stats"
  - Remove network_services.vnf_generic.vnf.prox_helpers.ProxSocketHelper.rx_stats

    * Remove the method which is unused and is marked as deprecated.

    Change-Id: Ie64084fcd26985283c664445b173a757d3d908ab
    JIRA: YARDSTICK-838
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index af3e090..3496600 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit af3e090dfcf2448d828308ca83ee79fdbd386245
+Subproject commit 349660091288e47c3c5032e6dec9d29e9a2f251f