Update git submodules

* Update docs/submodules/promise from branch 'stable/euphrates'
  - Update User Guide

    Change-Id: I939570ba3a2b8f7551e4d27700e494c5dc2edab7
    Signed-off-by: Bertrand Souville <souville@docomolab-euro.com>
    (cherry picked from commit d362639e2541bb6d37744a47e00e689e971ce541)

diff --git a/docs/submodules/promise b/docs/submodules/promise
index 639afda..76c4e4a 160000 (submodule)
--- a/docs/submodules/promise
+++ b/docs/submodules/promise
@@ -1 +1 @@
-Subproject commit 639afdab3b77466296b501f86f64f17e4c188c10
+Subproject commit 76c4e4a0bdde64bc36ad4bd0bdbeeb1251d3f4b8