Remove non exist static references.

[dzhuang]

Since the introduction of django-bootstrap-datepicker-plus, those links were no longer valid.

[inducer]

Thanks! These changes are already part of #892, which I am hoping to merge over the next week or so. As a result, I think I would prefer to merge them via that route. In fact, the only thing that's missing in #892 from my perspective are some rendering issues with the InlineMultiQuestion, specifically the various tooltip and right/wrong indicators. If you are able, it would be super helpful if you could take a look at that since you know that code better than me, and, perhaps, submit a PR targeting the bs5 branch.

[dzhuang]

Thanks. I guess the issue you mentioned is the removal of glyphicons in Bootstrap 5, I'll try to work on that in a few days.

[inducer]

It's not so much the glyphicons, it's all the popup/over/under logic and the field layout which has changed substantially in bs5.

[dzhuang]

This PR is closed in favor of #949.