Update git submodules

* Update docs/submodules/promise from branch 'master'
  - Add Masahito as Promise committer

    Change-Id: If607cfe7351413a006d55c3b2e7518bc6abaf47c
    Signed-off-by: Gerald Kunzmann <kunzmann@docomolab-euro.com>

diff --git a/docs/submodules/promise b/docs/submodules/promise
index 534c27e..a6ff265 160000 (submodule)
--- a/docs/submodules/promise
+++ b/docs/submodules/promise
@@ -1 +1 @@
-Subproject commit 534c27e67b3ed1f6213d97f49d7b95ec7777b647
+Subproject commit a6ff2653735c28bf478a1dda713bd1edea6cf378