Course has ended sticky alert padding causes UI bug with exercise anchor links

[khattam2]

Fixes #1311

Description

What?

Course has ended sticky alert padding causes UI bug with exercise anchor links

Why?

Exercises now result in a weird exercise frame UI bug after scrolling up:

How?

padding-top has been changed to margin-top

Testing

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[ihalaij1]

I edited the code so it doesn't use margin-top or padding-top at all.

Instead, it now waits until all AJAX requests have finished and then scrolls the page the height of the sticky alert, so that the content under it is no longer obscured.