Update jenkins/ath Docker tag to v5478 (#7504)

Co-authored-by: Nrenovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

ath.sh

@@ -6,7 +6,7 @@ set -o xtrace
 cd $(dirname $0)
 
 # https://github.com/jenkinsci/acceptance-test-harness/releases
-export ATH_VERSION=5458.v911b_2f0818ee
+export ATH_VERSION=5478.vb_b_cd04943676
 
 # TODO use Artifactory proxy?