Navigation - Add cypress tests for the inert attribute

[Mash707]

Describe the enhancement or change
Follow up to #11749. After the PR is merged we need to add cypress test for the inert attribute.

• click the expandable toggle to expand it, then tab() and assert that first item is focused
• click the expandable toggle to collapse it, then tab() and assert that the first item within that section doesn't have focus

[Mash707]

@thatblindgeye could you assign this to me.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.