Error message in error summary is not specific for questions in a repeating set (shows 'empty' message when 'invalid')

## Description

- To meet WCAG 2.1 A criteria, errors must be specific, identifiable and understandable.
- We addressed this in the past by adding a truncated portion of the question/field label.
- However this does not appear to carry over to repeating sets

## Steps to reproduce
1. Go to a form with required questions in repeating sets such as `cmd3h2gvz000eyj01pm3pskij`
2. Don't fill anything out when testing in draft mode and hit submit
3. See error summary with different formats for error messages:

## Details
- **Browser**: Chrome
- **Operating system**: Mac
- **Environment**: Staging
- **Language**: English and French
- **Viewport**: Desktop

## Expected behaviour

"Enter an answer for: {{Question label}}
_rather than_ the generic: "Complete the required field to continue." which could be listed a bunch of times and does not give a good enough indication of which question it relates to.