Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "[Horizon] Drop the obsolete Horizon workaround"
  - [Horizon] Drop the obsolete Horizon workaround

    Since we switch the Horizon package from
    Ubuntu/UCA repo to MCP repos,  we can drop the
    obsolete Horizon workaround.

    JIRA: FUEL-374

    Change-Id: I0b77a4f2158a972a5eb400919f2929c7bd8360cf
    Signed-off-by: ting wu <ting.wu@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 8a5df5e..dfe0808 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 8a5df5e7f886cfa27260d62a963fb0cb60d346ff
+Subproject commit dfe08086ac3d02a921bdd5cb3e52865396f1d774