Update text, increase visibility of refresh alert when tools are updated

[ssciolla]

Per feedback from the UX team, we need to update the text of the refresh alert to be "Refresh the page to update the tool's appearance in the left-hand navigation." Ideally, we also need to do something to make the alert more noticeable (probably through a snackbar/toast) if the user has scrolled down to where the top of the page isn't visible.

TEST PLAN:

• Choose a tool that already in the course site, click on the "REMOVE TOOL" button
• Verify the refresh alert message towards the bottom of the page -"Refresh the page to update the tool's appearance in the Course Navigation Menu.";
• Click the "X" to dismiss the message
• Then click on the "ADD TOOL" button to add the tool back to the course site
• The refresh alert message won't be displayed at this time since user has seen the message before.
• Refresh the browser. You will again see the refresh alert message once you Add or Remove a tool.

[ziegler1960]

tested on https://canvas-test.it.umich.edu/courses/587202/ Verified that the refresh message displays, message is dismissible, message does not re-display after adding back the tool, but does display after browser refresh and adding/removing more tools