Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - yamllint: Fix recently introduced errors

    Change-Id: If117588f7c43306959d29032b1d5eeb3c751dc44
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index db2144a..8401f25 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit db2144a7f6ed8586bbab39fdb5ea15b171388e85
+Subproject commit 8401f25a520843d884abb84806873baca0452ec8