Context:
The camunda maven repository was migrated to artifactory from nexus and a general new domain to reach the repo was introduced artifacts.camunda.com). Also see this announcement on slack.

However the current docs & the example repository contain links to the old nexus domain.

AT:

• all links to the nexus repo are replaced with artifactory equivalents in:
  https://github.com/camunda/camunda-optimize-examples
  https://github.com/camunda/camunda-docs-optimize

Justification:
Keeps our documentation up to date and allows users to get setup without error or our assistance