[core] fix(MenuDivider): remove tabIndex attr to resolve a11y failure

[bvandercar-vt]

Does not need tabIndex={-1}, role="separator" already makes it non-focusable. Having any tabIndex (even -1) causes this to fail aXe a11y tests, so we must remove it.

[adidahiya]

This tabIndex was added to fix a bug, you can see that via git blame: #6062

Can you fix the a11y issue without causing a regression re: #6054?

edit: in fact we even discussed this here: #6054 (comment)

[bvandercar-vt]

This tabIndex was added to fix a bug, you can see that via git blame: #6062

Can you fix the a11y issue without causing a regression re: #6054?

edit: in fact we even discussed this here: #6054 (comment)

Lol, I totally forgot I got involved in the discussion over this change... just to revert my decision later.

I do see that setting tabIndex={0} was the solution used for solving the #6054 bug, but I'm not sure why that worked, and I'm not sure if it was the ideal approach to solving that problem.

Regardless, it appears something has changed in the overall code between bug #6054 and now that has fixed the core of the problem— I cannot reproduce that bug, with or without my changes in this PR, and even if I remove the tabIndex. So, maybe that fix occurred between bp4 and bp5? Maybe it was fixed in Popover at some point? Either way, it's good news— it means that the core of the popover escape problem was solved, and we don't need the tabIndex anymore.

Here is a code sandbox from the latest blueprint codebase to show you: https://codesandbox.io/p/sandbox/jovial-matan-4w98xm?file=%2Fsrc%2FCoreExample.tsx%3A10%2C48 . As you can see, there is no tabIndex on the separator, and the bug no longer occurs.

[adidahiya]

ok, great, thanks for that code sandbox @bvandercar-vt. It looks like it is safe to remove this attribute.