Update git submodules

* Update docs/submodules/promise from branch 'master'
  - Switch promise from submodules to intersphinx

    Change-Id: I8feb0ba713e26fb112b32032703a7b1aeb75fc88
    Signed-off-by: Bertrand Souville <souville@docomolab-euro.com>

diff --git a/docs/submodules/promise b/docs/submodules/promise
index 7c28b66..2b4a1f6 160000 (submodule)
--- a/docs/submodules/promise
+++ b/docs/submodules/promise
@@ -1 +1 @@
-Subproject commit 7c28b66a376d8a441c40c2926b218497d63516a3
+Subproject commit 2b4a1f6c89a55c4003ecf6d7b9d58c801defad44