Remove an obsolete GN flag that had been used by SkParagraph (#24924)

Author: jason-simmons

tools/gn

@@ -108,12 +108,11 @@ def to_gn_args(args):
     gn_args['skia_use_fontconfig'] = args.enable_fontconfig
     gn_args['flutter_use_fontconfig'] = args.enable_fontconfig
     gn_args['flutter_enable_skshaper'] = args.enable_skshaper
-    if args.target_os == 'winuwp':
-      gn_args['skia_enable_winuwp'] = True
     if args.enable_skshaper:
       gn_args['skia_use_icu'] = True
-      gn_args['skia_enable_icu_ubrk_safeclone'] = True
       gn_args['flutter_always_use_skshaper'] = args.always_use_skshaper
+    if args.target_os == 'winuwp':
+      gn_args['skia_enable_winuwp'] = True
     gn_args['is_official_build'] = True    # Disable Skia test utilities.
     gn_args['dart_component_kind'] = 'static_library' # Always link Dart in statically.
     gn_args['is_debug'] = args.unoptimized