Update git submodules

* Update docs/submodules/promise from branch 'master'
  - Fix links to remove references to submodules

    All references to submodules must be removed for docs to
    work going forward.

    Can be tested once your project has a local tox file

    Change-Id: Ieb91d8f8f803599593b456a86ce4ed93c3951bbe
    Signed-off-by: Aric Gardner <agardner@linuxfoundation.org>

diff --git a/docs/submodules/promise b/docs/submodules/promise
index 2b4a1f6..91e36fd 160000 (submodule)
--- a/docs/submodules/promise
+++ b/docs/submodules/promise
@@ -1 +1 @@
-Subproject commit 2b4a1f6c89a55c4003ecf6d7b9d58c801defad44
+Subproject commit 91e36fd17d6843f38691ccf334ac863090ad65a1