Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - Minor updates to documentation

    Change-Id: I35b8069a0239858dad3b446f683d64140964fb42
    Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>
    (cherry picked from commit 4b163654de5efd0f4ad5dc5c88475f6fa2b4b8ae)

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 79379e8..5dffae8 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 79379e83773f17aefe65cbcfa9dbc70146d37984
+Subproject commit 5dffae89caf1baea043371883b76d40254b0097c