Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "[docs] Fix build warnings, minor alignments"
  - [docs] Fix build warnings, minor alignments

    - adopt NOTE tags;
    - switch some NOTE tags to WARNING;
    - use ``markup`` for all paths;

    Change-Id: If1bda281fd5cbef0b94110b59e02f41c443b0fb9
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 53c65e6..54ebfaf 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 53c65e66612ee71d4edd6e28896c16420bde2a6f
+Subproject commit 54ebfaf561693186580cacf259804f7968bec0fd