fix: redundant word 'navigation' in breadcrumb nav

[TheIceCreamBear]

Summary

Fixes #6581

Problem

(Originally discovered by inspecting the HTML of the webpage) Using the Windows 10 Narrator app, I visited the production MDN article about the navigation role. On this page, I navigated through the landmarks (Capslock + D) until I got to the breadcrumbs landmark, and it read out "Breadcrumb navigation, navigation landmark."

Solution

The solution was to remove the redundant word "navigation" from the aria-label of the affected nav element.

How did you test this change?

I followed the steps in the quick setup section of this repo's readme to load my change into the browser. I then followed the same steps as described in the section Problem. The narrator read the nav out as "Breadcrumb, navigation landmark."