Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "[XCI] Remove inventory for prepare-tests.yml"
  - [XCI] Remove inventory for prepare-tests.yml

    We are finally fetching all ODL variables from inside the scenarios.
    Therefore, we don't need to use the inventory:

    ${XCI_PATH}/.cache/repos/openstack-ansible/inventory/dynamic_inventory.py

    Change-Id: I91d17cb899a037887bc97441a1c1e37ff57b4850
    Signed-off-by: Manuel Buil <mbuil@suse.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 738793f..c0c28db 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 738793f4c8cda893f84dba6081f952627af772d5
+Subproject commit c0c28db9493e0a01edb2050a3ce6ce72d6636071