aspect ratio of navigation button background is not a circle

[lucidNTR]

Did you search for similar issues before submitting this one?
yes

Describe the issue you encountered:
When you hover over an active forward or backward button, the white background is not circular but slightly eliptical.

Expected behavior:
the button should be a nice circle

• Platform (Win7, 8, 10? macOS? Linux distro?):
  macOS
• Brave Version:
  master
• Steps to reproduce:
  1. open page
  2. navigate to any link
  3. hover over back button
• Screenshot if needed:
  
  

[bradleyrichter]

new rectangle style allows closing of this issue