4.20.9 - Fix headless UC Mode, and other updates

Fix headless UC Mode, and other updates

• Fix headless UC Mode (caused by missing args)
  --> This resolves #2230
• Update "omnibox" preferences
  --> This resolves #2231
• Refresh Python dependencies

What's Changed

• Fix headless UC Mode, and other updates by @mdmintz in #2232

Full Changelog: v4.20.8...v4.20.9