(Accessibility) Remove mention of deprecated EuiKeyboardAccessible

[myasonik]

EuiKeyboardAccessible was deprecated because it was abused more often than it was used successfully so we need to remove it from Kibana before December 2020.

It doesn't seem like it's actually used but it is mentioned here: https://github.com/elastic/kibana/blob/master/x-pack/plugins/security_solution/public/resolver/view/process_event_dot.tsx#L273-L276

If the comment is just outdated, please remove it to avoid confusion. But there is concern that something in such a brittle DOM/ARIA structure may not be working currently if EuiKeyboardAccessible was assumed to be there somewhere and isn't.

[alexwizp]

EuiKeyboardAccessible has been removed in #69098. No more imports from Kibana. Looks like this issue is obsolete and can be closed.