Fix work item labels in create

What does this MR do and why?

Fixes issue with searched labels in the work item create flow

Fixes #480523 (closed)

MR acceptance checklist

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Enable work_item_epics work_item_epics_rollout work_items_beta
2. Open a group with > 100 labels (alternately add first: 5 to the query in app/assets/javascripts/sidebar/components/labels/labels_select_widget/graphql/group_labels.query.graphql to simulate page limit)
3. From the navigation "+" menu select "Create epic" — you should see the create modal
4. Add labels that do not appear in the first page of label results
5. Confirm the labels were selected, save epic, confirm labels are there

Related to #480523 (closed)