[VPAT] TextFormField sample's content shouldn't be a list #194237

b/570424970

STEPS TO REPRODUCE:

Turn on TalkBack.
Swipe to the text.
Observe the screen reader announcements.
Element Description: TextFormField

Element location: https://github.com/flutter/packages/blob/main/packages/material_ui/test_apps/a11y_assessments/lib/use_cases/text_form_field.dart

OBSERVED RESULT: Content is not a list but it is marked as such. TalkBack announces

Editbox, Enabled text form field Email, 1 of 3, in list 3 items
xyz, Disabled text form field Email, Disabled, 2 of 3
@gmail.com, 3 of 3
Submit, button, 4 of 3