Update git submodules

* Update docs/submodules/promise from branch 'stable/danube'
  - Update doc structure to better fit release notes:
     - There is no need for heading "Manual testing"
     - Update to user guide abstract

    Change-Id: I30606c77c37ef39afba64dd560ff2a554e2cc10e
    Signed-off-by: Gerald Kunzmann <kunzmann@docomolab-euro.com>
    (cherry picked from commit 927078e6569121789e3e488d1599c6c1f30fcf8b)

diff --git a/docs/submodules/promise b/docs/submodules/promise
index bc4f406..92bd641 160000 (submodule)
--- a/docs/submodules/promise
+++ b/docs/submodules/promise
@@ -1 +1 @@
-Subproject commit bc4f406e0fd52b2712f25c442940710bfc686705
+Subproject commit 92bd641d511dd52ab73122842f616ec2b6fc1c24