Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Update Gambia Challenges presentation

    It will be interesting to verify installers via
    opnfv/functest-components too.

    Change-Id: Ib5da2e35bce5f8a7013ad42b82b2f0e416129863
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/functest b/docs/submodules/functest
index 99d75d8..b20211a 160000 (submodule)
--- a/docs/submodules/functest
+++ b/docs/submodules/functest
@@ -1 +1 @@
-Subproject commit 99d75d87e31d4f9e078c899bd643da5474963aba
+Subproject commit b20211aedd531e0d4875fde9e618c25faa8721e8