Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Locate toplevel for git submodule [2]

    Change-Id: I0c719ec4cfd3d0a526fd6913358cc80c5a599985
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index bb4d411..936b4c7 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit bb4d411c652dd37b17ab69c85ae75d50fe815561
+Subproject commit 936b4c7df84cc725924c62b2ca3dc5e89509ba50