Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - Update the reference for scenarios

    Modified the reference link for the scenarios as it colides with
    another installer. To be used with https://gerrit.opnfv.org/gerrit/#/c/45795

    Change-Id: I7b55cfdb877715ec4fa0292adc11e36b7cf4ae53
    Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>
    (cherry picked from commit aa0f463972db10c96ea61f7f7067477ad28b6482)

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 36c6f5a..5638ff1 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 36c6f5a54806a4ab21f33d24256c558dc65a4157
+Subproject commit 5638ff11b251a2901886c07fa58d31ea53cd217d