Docs feedback: Replace link to DAG description

Link the doc and describe what is wrong with it. https://docs.gitlab.com/ee/ci/directed_acyclic_graph/index.html

The link to https://www.techopedia.com/definition/5739/directed-acyclic-graph-dag should be replaced with a link to another page because the DAG description is just plain wrong.

Suggested replacements:

• https://hazelcast.com/glossary/directed-acyclic-graph/
• https://en.wikipedia.org/wiki/Directed_acyclic_graph