Update git submodules

* Update docs/submodules/daisy from branch 'stable/euphrates'
  - [docs] Refresh reference for opnfv-5.1.0

    Change-Id: I0ef56ea85f4c401064a8cc4baf9672dc58521193
    Signed-off-by: Zhijiang Hu <hu.zhijiang@zte.com.cn>

diff --git a/docs/submodules/daisy b/docs/submodules/daisy
index 1c3c253..691fa29 160000 (submodule)
--- a/docs/submodules/daisy
+++ b/docs/submodules/daisy
@@ -1 +1 @@
-Subproject commit 1c3c253f906e76b76f207f64c03a2c14c48647a1
+Subproject commit 691fa291aca3a4d969ce1f6ab1f7335b54cde78a