Activate light mode and set bottom border for navbar

• Type: Task
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: None
• Fix Version/s: None
• Component/s: Web Search > Search Admin
• Labels: None
• Epic Link: Activate separation line in light mode nav-bars

None of the Search Tuning applications has the light mode active for their navbars.

Please activate it and review the bottom border.