Update git submodules

* Update docs/submodules/fuel from branch 'stable/danube'
  - [tacker] Adjust tackerc to v3 of identity api

    JIRA: FUEL-267
    Change-Id: Ia0e9ed3298681319c870132628d930175e084bc0
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>
    (cherry picked from commit 5db425bc2b0a2c44dc9fdcfbec19afaa9ecc442a)

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 9e78ba7..6c24adf 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 9e78ba77a04219512bae5b0855b573ab03b6c1a5
+Subproject commit 6c24adf6e75cc0e7dc0fb8ed81fe1fd4bc56bdc5