Documentation fix: add white space for code block (#1657) #1788

Job	Run time
build-docker (internet.nl, docker/Dockerfile, app)	1m 6s
build-docker (unbound, docker/Dockerfile, unbound)	1m 9s
build-docker (linttest, docker/Dockerfile, linttest)	59s
build-docker (test-runner, docker/test-runner.Dockerfile)	56s
build-docker (webserver, docker/webserver.Dockerfile)	1m 22s
build-docker (grafana, docker/grafana.Dockerfile)	1m 19s
build-docker (util, docker/util.Dockerfile)	57s
integration-test	3m 33s
lint/check	52s
development-environment-test	2m 17s
docs	1s
test	2m 13s
batch-integration-test	2m 46s
	19m 30s

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