Remove IS_EE flag from app/assets/javascripts/monitoring/components/dashboard.vue
After https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/30351 has landed, we have just a few usages of IS_EE
and we probably can change the usage by e.g. utilizing ee_else_ce
instead. This issue is to track removal of the usage from app/assets/javascripts/monitoring/components/dashboard.vue