fix(a11y): icon button-black focus outline does not meet 3:1 contrast…

… minimum in dark theme (#297)

## PR Checklist

Please check if your PR fulfills the following requirements:

- [ ] Tests for the changes have been added (for bug fixes / features)
- [ ] Docs have been added / updated (for bug fixes / features)
- [ ] If applicable, have a visual design approval

## PR Type

What kind of change does this PR introduce?

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- [x] Bugfix
- [ ] Feature
- [ ] Code style update (formatting, local variables)
- [ ] Refactoring (no functional changes, no api changes)
- [ ] Build related changes
- [ ] CI related changes
- [ ] Documentation content changes
- [ ] clarity.design website / infrastructure changes
- [ ] Other... Please describe:

## What is the current behavior?

<!-- Please describe the current behavior that you are modifying, or
link to a relevant issue. -->

Issue Number: [CDE-1604](https://jira.eng.vmware.com/browse/CDE-1604)

## What is the new behavior?
The focus outline colour defaults to the `webkit-focus-ring-color` in
dark theme on windows chrome.

## Does this PR introduce a breaking change?

- [ ] Yes
- [x] No

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and migration path for existing applications below. -->

## Other information

Co-authored-by: Andrea Fernandes <[email protected]>

projects/core/src/button-action/button-action.element.scss

@@ -107,5 +107,6 @@ cds-icon,
 @media (-webkit-min-device-pixel-ratio: 0) {
   :host(:focus) .private-host::after {
     outline-color: -webkit-focus-ring-color;
+    outline-style: auto;
   }
 }