bug(Button): Firefox accessibility tree error on tertiary variant

[tujoworker]

As seen above:

It only is an issue displayed in the FF a11y tree. Axe nor Chrome dev tools do show anything about it.

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There are two issues, the yellow and the red:

1. The red is cause by the usage of :after, which is again implemented via buttonFocusRing.
2. While the yellow is caused by outline: none;

Both are only throwing, as long as the code is wrapped inside :focus-visible (@include focus-visible). When using @include focus, the issue is not present anymore.

The code above is inside button--tertiary.scss.

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I assume that it is not a real issue. But to be sure, we should check with VoiceOver and NVDA. But my assumption is that it reports a potential "visual" issue.