Show rolled up dates on epic route

What does this MR do and why?

Show rolled up dates on epic route

We did not push the feature flag from the epic controller to the frontend. Therefore we did not show the rolledup dates feature when serving the work item on the epic route.

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Before	After

How to set up and validate locally

1. Enable work_item_epics, work_item_epics_rollout, work_items_rolledup_dates feature flags
2. Create an epic
3. Go to the /work_items/:iid route for the epic -> see that it shows the radio buttons for dates for either fixed or inherited
4. GO to the /epics/:iid route for the epic -> see that it shows the radio buttons for dates for either fixed or inherited (this didn't work before this change)