Update git submodules

* Update docs/submodules/promise from branch 'stable/danube'
  - Remove numbering

    Change-Id: Ia96a2761dc5a44a48e35816b7adb28222a962adc
    Signed-off-by: Gerald Kunzmann <kunzmann@docomolab-euro.com>
    (cherry picked from commit 41c803455971d76e7a6d8cd9cde3371525138db9)

diff --git a/docs/submodules/promise b/docs/submodules/promise
index 92bd641..13ebd0c 160000 (submodule)
--- a/docs/submodules/promise
+++ b/docs/submodules/promise
@@ -1 +1 @@
-Subproject commit 92bd641d511dd52ab73122842f616ec2b6fc1c24
+Subproject commit 13ebd0c0f1c23f822633185ceb772289d219b65e