Roll Dart SDK from 28bc810020c9 to 259559ba5091 (1 revision) (flutter#34445)

Author: skia-flutter-autoroll

DEPS

@@ -45,7 +45,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/main/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '28bc810020c9f9e4b1833c4f09b34ad621c032d4',
+  'dart_revision': '259559ba5091c1d9dbbf4b758e921d169dd78e79',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py