Dismissable popover color conflicts with a:not[href])

[ffoodd]

Next to #29140, we now have a conflicting style in dismissible popovers since it has no [href] and its styles rely on a single class specificity:

https://twbs-bootstrap.netlify.com/docs/4.3/components/popovers/#dismiss-on-next-click

I'm not quite sure about the solution for this:

• re-introduce :not([tabindex]), which would reintroduce what @ysds wanted to remove;
• use !important on .btn-* variants (ugh)?
• force color by using .text-white in that case?
• anything else? Maybe using colored links or something?

And moreover, is there any other case of links without target styled as buttons?

[mdo]

This button is lacking an href and should likely just be converted to a <button> element. That'd fix the issue I think?

[ffoodd]

@mdo Indeed! Noted this quickly while theming things around, but should definetely be a button!

[ffoodd]

It's been fixed in v5 and backport in progress to v4.