Term list is not updating when using Gutenberg

[stevegrunwell]

When using the block editor (Gutenberg), the list of available terms is not being updated without a full-page refresh.

Steps to reproduce

1. Attempt to create a new post using Gutenberg and assign a category
2. After assigning a category, check the "Promote Post" panel

Expected Behavior

The newly-assigned category should be available for selection under "Promote Post"

Observed Behavior

The newly-assigned category is missing from the list.

Reference: https://wordpress.org/support/topic/update-for-gutenberg-3