[stable34] fix: make unified filter chip accessible

[kristian-zendato]

• Resolves: [core] unified search chips are not in tab sequence #58385

Summary

The remove control on unified search filter chips was a plain <span> with a click handler: it was not keyboard-focusable and had no accessible name, so screen reader and keyboard users could not remove an active filter.
This changes the control to a real <button> and adds a translated aria-label ("Remove filter: {text}") so assistive technology announces which filter will be removed. Styles were adjusted so the button keeps the previous visual appearance

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI