Follow-up to #12914

jablib/src/main/java/org/jabref/logic/cleanup/ConvertMSCCodesCleanup.java needs to be converted to a class implementing org.jabref.logic.cleanup.Formatter.

Should be removed from the list of hard-coded check boxes and moved to the field formatter list:

Background:

The contents in "Miscellaneous" are working multi-field, whereas "field formatters" work single field

I know the UX is bad for the formatters, but with the current implementation, the UI gets even more cluttered.