Remove api/HTMLTableDataCellElement.json

HTMLTableDataCellElement never actually existed in browsers; instead it
existed only in the HTML spec — before being removed in
whatwg/html@e383ae2:

> Ever since the dawn of HTML
> (whatwg/html@2ac31bb) there have been two
> table cell interfaces, HTMLTableDataCellElement for <td>, and
> HTMLTableHeaderCellElement for <th>. No browser ever implemented this
> split, instead using the single HTMLTableCellElement interface. This
> aligns the spec with browser reality.

See also whatwg/html#1115

> Can we remove the HTMLTableDataCellElement/HTMLTableHeaderCellElement
> fiction? UAs just have HTMLTableCellElement.