Progress modal isn't showing for syncing

[jayoshih]

Original report

"Sync resources" - happening in the background but needs indicator on the channel editor UI

[jayoshih]

Might be related to #2688

[rtibbles]

Fixed in #2909

[metodimilevqa]

@rtibbles @marcellamaki @jayoshih I confirm the fix verification is successful. Tested at: https://hotfixes.studio.learningequality.org/