Fix: Adminbar: Unnatural focus outline in frontend

[hbhalodia]

Trac ticket: https://core.trac.wordpress.org/ticket/65177

Description

• Admin bar on wp-admin page was having outline set as 0, but on frontend the default outline was being shown which was having inconsistency with admin page admin bar.
• PR aims to remove the outline from the frontend admin bar, which mimics exactly the admin bar on wp-admin side.

Screenshots

Before	After

Use of AI Tools

• None

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[t-hamano]

Thanks for the PR. However, we cannot simply remove the outline because it is necessary in Windows High Contrast mode, as the text and background colors do not change when focused.

You can test this issue by opening the developer tools in the Chrome browser, accessing "More Tools", "Rendering", and "Emulate CSS media feature forced-colors", and changing it to "forced-colors:active".

In WordPress, transparent outlines are sometimes used to solve this type of problem. This approach takes advantage of the characteristic that transparent outlines are not visually displayed, but they become visible in Windows High Contrast Mode.

Based on this, it should be sufficient to simply make the following changes.

#wpadminbar a:focus {
	outline-offset: -1px;
	/* Only visible in Windows High Contrast mode */
	outline: 2px solid transparent;
}