Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - [baremetal] MaaS: Remove curtin netconfig via Salt

    JIRA: FUEL-301

    Change-Id: Id6b2b423b8045c581fa5c02133cf91702d9915c9
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
    (cherry picked from commit 4010ea45c703d82e2fb95dcc869ff72bbca088b7)

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index b7166b8..ee21bd7 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit b7166b84b24bcccdfcd46eb485249ef17b953b81
+Subproject commit ee21bd791dd74558254f2b4aaef15504c9d395ea