Display credentialing status on event management page. Fixes #2163.

[tompollard]

As discussed in #2163, the "credentialed" column on the event management page should display whether or not an event participant is credentialed.

As a result of a bug in the template, the credentialing status is not displayed. This pull request is a minor update to fix the bug. I also remove a couple of unused columns at the same time (e.g. "co-host").

[tompollard]

@mscanlan-git please could you test this and merge if you are happy? To test:

1. Run git pull to pull down the branch
2. Check out the branch (git switch tp/event_credentialed)
3. Run the local server as usual. Check that the credentialing status is now displayed correctly (rgmark and aewj are credentialed users).

We need to think more about whether displaying the credentialing status is enough. For example, should we also display:

1. training status?
2. details on which DUAs have been signed?

I think we should raise a new issue to discuss these points (and address them in a later pull request).

[mscanlan-git]

Thanks @tompollard, this is working as intended.

I do think we should have a column for training status and DUAs, as these are two additional requirements that users will need to complete. Having all 3 columns available to the event host will make it easier to pinpoint why a user is unable to access the datasets for that event. I will create an issue to note.

[tompollard]

Thanks Michael! I have pushed the fix to the live server.