updated Android launcher icons (#5238)

examples/flutter_gallery/README.md

@@ -22,9 +22,5 @@ The `flutter run --release` command both builds and installed the Flutter app.
 
 ## Icon
 
-Icon was generated using Android Asset Studio:
-https://romannurik.github.io/AndroidAssetStudio/icons-launcher.html#foreground.type=image&foreground.space.trim=0&foreground.space.pad=0.1&foreColor=607d8b%2C0&crop=0&backgroundShape=square&backColor=ffffff%2C100&effects=none
-
-From the Flutter Logo:
-https://github.com/flutter/website/blob/master/_includes/logo.html
-which appears to be CC-BY 4.0.
+Android launcher icons were generated using Android Asset Studio:
+https://romannurik.github.io/AndroidAssetStudio/icons-launcher.html#foreground.type=image&foreground.space.trim=1&foreground.space.pad=0.1&foreColor=607d8b%2C0&crop=0&backgroundShape=square&backColor=fafafa%2C100&effects=none