Desktop: Sidebar: Remove redundant focus indicator

[personalizedrefrigerator]

Summary

This pull request removes the orange focus outline for notebooks and tags in the sidebar. Focus is already indicated with a different background color.

Before

After

Testing plan

1. Click on a notebook in the sidebar.
2. Use the arrow keys to navigate to the "Tags" heading.
   • The "Tags" heading should still have an orange focus outline.
3. Use the arrow keys to navigate to a tag in the sidebar.
   • The tag should have a darker background, but no orange focus indicator.