Inconsistent documentation for /api/events return values
Steps to reproduce
According to the documentation on `https://docs.opencast.org/develop/developer/api/events-api/#get-apievents`, the JSON representation of an event in `/api/events` should include a `presenters` field.
Opencast onl yreturns a `presenter` field instead.
This seems to be a typo in the code, because `presenters` would be more consistent with the naming of other fields. To prevent unnecessary compatibility breakage, I propose to only update the documentation to use `presenter`. It's not user facing, so not really that important.