Accessibility: Improve and modernize user interface controls: Revert the new links focus style.

Thew new dotted outline for the links focus style introduced in [46241] doesn't appear to be ready to guarantee a good indication of focus.
It was agreed to restore the previous links focus style and postpone exploration for a new style to the next release cycle.
Partially reverts [46241] and [46293].

See #34904, #47153.

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git-svn-id: https://core.svn.wordpress.org/trunk@46223 1a063a9b-81f0-0310-95a4-ce76da25c4cd