Update links in assessment catalog pages #154

In the assessment catalog pages (https://www.prairielearn.com/catalog/assessments/homework, https://www.prairielearn.com/catalog/assessments/exam, etc.), the links to the corresponding pages are outdated. I believe they are still pointing to the old demo course instead of the example course links. The PrairieLearn content has the updated links (see PrairieLearn/PrairieLearn#14625), so I assume the issue is that the PrairieLearn submodule is extremely outdated.

This was brought up on Slack: https://prairielearn.slack.com/archives/C266KEH9A/p1779823659491599.