Metadata dialog does not highlight selected field when using tab or arrow keys

[fugidev]

Guidelines

• [X] I have read the guidelines.

Version/Commit hash

a7db3db

Describe the bug.

1. Click on 'File > Export > Export as MP3'
2. Select path and click 'Save'
3. Try to navigate the text fields of the 'Edit Metadata Tags' Dialog using tab or arrow keys
4. Observe: the selected field is not hightlighted, however editing works as expected

Expected behavior

When navigating these text fields using a keyboard, the currently selected field should be highlighted by an outline (like clicking a field does) or something similar.

OS

Windows 10, Ubuntu 20.04

Additional context

It does work as expected on macOS, and also in Audacity - I suspect this was caused by a design change.

This issue is not a duplicate

• [X] I have confirmed this issue isn't a duplicate.