Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - fix for documentation: correct git checkout tag is opnfv-5.0.2

    Change-Id: I2c4192d4dc299d167ba6b1b9db91c6d73c87c417
    Signed-off-by: Mika Rautakumpu <mika.rautakumpu@nokia.com>
    (cherry picked from commit 6cb5e8ee2deeda4b08cefe8925078410994d084f)

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 5dffae8..a649315 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 5dffae89caf1baea043371883b76d40254b0097c
+Subproject commit a64931567c37a2fa551ca21e8382259a3c4814c7