Fixes #69025

Quick PR to add a missing ARIA role.

What?

Semantically, the list of blocks in Styles > Blocks is a series of list items but it misses a wrapping list.

Why?

This is equivalent to a series of <li> elements with no wrapping <ul> element and impacts the way screen readers are expected to announce the list itself, the amount of items and position.

How?

Adds role="list" to the wrapping element.

Testing Instructions

• Repeat the steps from the issue Global Styles: the list of Blocks in the Styles panel is a seeries of lisitems with o wrapping list #69025
• Observe the items are now wrapepd within an element with role="list".

Note: if you like and if you use Chrome, you can switch the DOM inspector to the accessibility tree view to better check the correct semantic structure:

Testing Instructions for Keyboard

Screenshots or screencast