Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "Update release notes for 5.1"
  - Update release notes for 5.1

    The release notes are updated with relevant Jira filters and
    changes since 5.0

    Change-Id: If14cb0369ced899d17608ef43e93b848e8b2a5c8
    Signed-off-by: Cristina Pauna <cristina.pauna@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 8d4c328..ef1c113 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 8d4c3285d86ece6a25609ccb207ac5fb903d1d28
+Subproject commit ef1c1131020e45bd280f2ef158f5416552f190e0