fix(ui5-shellbar): improved samples accessibility

[plamenivanov91]

Additional acc roles are added to the profile button's popover.

Fixes: #8821

[yanaminkova]

I suggest maintaining the current role for now, since the accessibility specification is not explicit about what it should be. You can suggest to the reporter that if their request is urgent, they could specify the roles themselves, as you have already done in this change. Additionally, consider lowering the priority of the ticket. Meanwhile, we can consult with the accessibility expert responsible for the screen reader specification and if we obtain their agreement and once the specification is updated, we can proceed to update the sample accordingly.

[yanaminkova]

Following consultation with the accessibility expert responsible for the screen reader specification, it has been determined that the correct approach in this scenario is to adjust the accessible-role of the ui5-popover containing the list to "None." Currently, it retains its default role as "Dialog," which is unsuitable for containing a menu. Consequently, the ui5-list and the ui5-li should be appropriately designated as "menu" and "menuitem," as you have already done.