Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Prune docker images on ericsson-build3

    This patch removes ericsson-build5 as well since that machine
    does not exist anymore.

    Change-Id: I7598e5fff166e29ecf4fcd18bebc6d2e3b9be9ed
    Signed-off-by: Fatih Degirmenci <fdegir@gmail.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 3f84461..dc4cda2 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 3f84461f80baa8c0c039071678523e03e2d4651c
+Subproject commit dc4cda2e9ee9d29396c88cf85ead84d58eaadf20