Accessibility - Missing link-name on notification close

[stromb0li]

Affected version

XF 2.2

Really minor, but the "x" on notifications is missing a title to pass accessibility compliance testing.
WCAG 2.4.4, WCAG 4.1.2

Given it doesn't contain text, the element should have the aria-label or aria-labelledby attribute.

This is reproducible on the xenforo website with the notification banner in the bug report section here.