Table showcase documentation has minor error

[TiPunch69]

The showcase documentation for editing tables has two minor errors:

• it does not state that for row editing, the parameter editmode="row" has to be set (as in the Github example). So the case in the documentation does not work

• In the table documentation overview page the wrong source is given in the onRowEditCancel function: it should be cars, not cars2. This is a copy and paste error from the detailed documentation/github showcase example.