Update git submodules

* Update docs/submodules/dovetail from branch 'master'
  - Remove obsolete developer documents

    Some developer documents are now old and suggested to be removed.

    Change-Id: Ifa26a1535d57a560a0525eafa300ae087feb3191
    Signed-off-by: Eddie Arrage <eddie.arrage@huawei.com>

diff --git a/docs/submodules/dovetail b/docs/submodules/dovetail
index 73f332f..d978ea0 160000 (submodule)
--- a/docs/submodules/dovetail
+++ b/docs/submodules/dovetail
@@ -1 +1 @@
-Subproject commit 73f332fc513f184513be483db6a108bd3c7b7d9b
+Subproject commit d978ea0994d79164e6573415355f2ad0ae08effa