Allow more ARIA attributes that are string values to be empty

[WilcoFiers]

There are a few newer ARIA attributes of type: string that I think should be allowed as empty:

• aria-braillelabel
• aria-brailleroledescription
• aria-valuetext

Since both aria-label and aria-roledescription are allowed to be empty, I see no reason why their braille equivalents shouldn't be. As for valuetext, it seems fairly reasonable that values can be empty, so aria-valuetext should be allowed empty too.

[padmavemulapati]

validated using latest axe-core develop branch code base,
braille equivalent rule also allowing
aria-braillelabel
aria-brailleroledescription
aria-valuetext allowing empty

Recording tells us allowed and fail conditions of the checks:

Screen.Recording.2023-08-03.at.2.49.14.PM.mov