fix(_form-fields.scss): added two style updates for validated form fields

[Bob-E]

Forms – Client side validation fields - Focus state increases the border, causing jump

Description

A couple client side validation fields got skipped when working on UDS-1474: 2.9.1:Forms – Focus state increases the border, causing jump, so this is to add the 8px bottom border to the remaining 2 field styles. (Note: This is already being done in WS2-1633)

Links

• Unity reference site
• JIRA ticket
• Unity Design Kit

Checklist

• [x] Unity project successfully builds from root yarn install & yarn build
• [x] Commits do not contain multiple scopes
• [x] Add/updated examples
• [x] Add/updated READMEs/docs
• [x] No new console errors
• [x] Accessibility checks

Browsers

• [x] Chrome
• [x] Safari
• [x] Firefox
• [x] Edge