Improve clarity of apply-updates icon in Notebook

[esanzgar]

In the Notebook, a refresh icon appears every time there is new or updated annotations for the selected group:

There was a Slack conversation about replacing the icon for a more textual variant: https://hypothes-is.slack.com/archives/C0C6BDS1H/p1618395779016200

[dwhly]

Thank you @esanzgar ... just dropping reference to another earlier discussion here for easy reference. https://trello.com/c/tRZ2H7iH/452-defer-applying-realtime-updates