Sidenav: Unable to navigate pages using keyboard

[francinelucca]

Description

A user can navigate through the sidenav treeview using the keyboard but when trying to go to a page by pressing enter, the item in the treeview is focused but the browser does not navigate

Steps to reproduce

How do we reproduce the error? Please be as specific as you can.

1. https://next.carbondesignsystem.com/
2. Tab into sidenav
3. Use arrow keys to navigate to an item that isn't currently selected
4. Press enter
5. notice browser does not navigate