feat: Add visual indicator for closed courses

[swayam-agrahari]

NOTE: Please review the pull request process before opening your first PR: https://github.com/WikiEducationFoundation/WikiEduDashboard/blob/master/CONTRIBUTING.md#pull-request-process

What this PR does

This PR introduces a visual indicator for courses that have been "closed out" by Wiki Education staff.

Screenshots

Before:

After:

closes #6050

Open questions and concerns

Please let me know if this works or if further changes are needed!

[ragesoss]

This looks great! I don't think the 'All review work...' half of the message is needed. Admins who will see this know what 'closed' means.

Showing a 'closed' indication on the campaign view is also a good idea, but I'd prefer leaving that to a separate PR. I will add notes about how that ought to work, on the issue description.

[swayam-agrahari]

@ragesoss
Thank you for the feedback!
I will remove the "All review work..." sentence as suggested. For the campaign view 'closed' indication, I can handle it in this PR if you'd prefer.
If not, do I need to raise an spearate issue for campaign view,if not included in this pr?
Let me know how you'd like me to proceed!

[ragesoss]

I prefer a separate PR, but you can mention the same issue for the campaign view.

[swayam-agrahari]

Hello @ragesoss , I have removed the additional texts and styles from campaign view.
I will make a pr for campain view asap : )