Include tasks in Milestoneish sorted items

What does this MR do and why?

Recently, as part of rolling out Milestone widget on Epic Work Items, this MR was shipped to swap out the use of IssueFinder for the Milestone report page to WorkItemsFinder.

As part of this, we conditionally included epics as part of the work item types input to the finder based on the state of work_items_alpha FF. However, this caused a regression which excluded tasks from the Milestone report page in either case. This MR alters the check to include tasks in the returned items via WorkItemsFinder.

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Setup a group Milestone locally and assign 3 work items to it. One should be an Issue, one should be an Epic, and one should be a Task
• With work_items_alpha feature flag enabled, load the milestone report page and you should see all 3 work items

screenshot

• Now disable work_items_alpha FF and reload the page, you should only see the Issue and the Task, not the Epic

screenshot

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Related to #537277 (closed)