Update git submodules

* Update docs/submodules/promise from branch 'stable/euphrates'
  - Remove extra '+' in api_mapping table

    This is breaking latex/PDF generation as the parser thinks an extra row
    is missing from this table.

    Change-Id: Ic814f02d9d51b14c7590002565fe07f5e5d8f043
    Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>

diff --git a/docs/submodules/promise b/docs/submodules/promise
index 4fce836..889d321 160000 (submodule)
--- a/docs/submodules/promise
+++ b/docs/submodules/promise
@@ -1 +1 @@
-Subproject commit 4fce83663cfbfc6ee7be35ca8ef5ae5c96ec56a7
+Subproject commit 889d321b6cf404d9c500ad584f975c01b14460fb