Reland "Remove GN staging flag for save layer bounds" (flutter#42029)

Reverts flutter/engine#42026

After investigating, this is a bug fix for the scubas.

Author: Casey Hillers

tools/gn

@@ -300,8 +300,6 @@ def to_gn_args(args):
   gn_args['skia_use_wuffs'] = True
   gn_args['skia_use_expat'] = args.target_os == 'android'
   gn_args['skia_use_fontconfig'] = args.enable_fontconfig
-  gn_args['skia_use_legacy_layer_bounds'
-         ] = True  # Temporary: See skbug.com/12083, skbug.com/12303.
   gn_args['skia_use_icu'] = True
   gn_args['is_official_build'] = True  # Disable Skia test utilities.
   gn_args['android_full_debug'