fix(a11y): Add keyboard accessibility for scrollable content in About tab

[Copilot]

Issue

The scrollable content area in the "About" tab was not accessible via keyboard navigation, as outlined in issue #7280. This prevented keyboard users from accessing important information displayed in the scrollable region.

Changes

This PR adds proper keyboard accessibility to the scrollable content in the About tab panel by:

1. Adding tabIndex={0} to the scrollable container to make it keyboard focusable
2. Adding aria-label to describe the content area for screen readers
3. Updating tests to accommodate these changes

These changes ensure that users relying on keyboard navigation can now access all information within the About tab panel, following WCAG 2.1.1 success criteria (Keyboard) and in alignment with the best practices outlined in our accessibility documentation.

<div 
  className="msla-panel-content-container" 
  tabIndex={0} 
  aria-label={intl.formatMessage({
    defaultMessage: 'Scrollable content',
    id: 'panelScrollable',
    description: 'Accessible label for the scrollable content area in the panel'
  })}
>

Fixes #7280.

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[hartra344]

This has broken the end to end tests, can you run those tests find the errors and fix them?

[Copilot]

This has broken the end to end tests, can you run those tests find the errors and fix them?

I've fixed the issue that was causing end-to-end tests to fail. The problem was a mismatch between the string ID used in the panel component (DxykM0) and the ID defined in the strings.json file (panelScrollable). I've updated the code to use the correct ID that matches the strings file. This should resolve the test failures.