ESR115: change devicePixelRatio spoof to 2 in alpha for testing

links

• https://github.com/mullvad/mullvad-browser/issues/75 - Blurry elements on some websites
• 1554751 - Consider to change the spoof value of window.devicePixelRatio

then upstream if no issues reported .. I think 4 years is long enough. It's literally a single char change. Good first patch 😄