Data breach form has mismatched text size for labels

[WilliamWDTK]

The label for the special category checkbox on the /help/report-a-data-breach form appears larger than the other form fields. Inspecting the HTML, this appears to be due to the presence of the form_label class on that element, but not on the others on that form.

Cross-referencing with other forms we have, it would appear that we probably want the form_label on all relevant elements on that form.