.dialog should have 'outline: none' on focus

[luixxiul]

Test plan

#10557 (comment)

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Describe the issue you encountered: .dialog should have 'outline: none' on focus. Otherwise:

• Platform (Win7, 8, 10? macOS? Linux distro?): Debian and Windows

• Brave Version (revision SHA): at lease since 0.17.19. the issue became noticeable as the dialog shadow was removed on 0.18.x. On 0.17.19 you get the orange focus ring as this shows:

  

  The issue has not been almost noticeable on Windows as the focus ring of the dialog appears exactly over the application window's border:

  

• Steps to reproduce:

  1. Open a site
  2. Click the lion icon

• Actual result: See above

• Expected result: the focus ring should be removed from .dialog on dialog.js

  browser-laptop/app/renderer/components/common/dialog.js

  Line 74 in 3d2b641

  dialog: {

• Will the steps above reproduce in a fresh profile? If not what other info can be added?

• Any related issues:

[luixxiul]

It actually can be reproduced on Slack Desktop app (both on Windows and Debian). I assume this is a common issue among electron based apps.