Fix dartdoc typo (flutter#14772)

mravn-google · web-flow · commit 54bf773d376d · 2018-02-19T20:35:53.000+01:00
diff --git a/packages/flutter/lib/semantics.dart b/packages/flutter/lib/semantics.dart
@@ -10,7 +10,7 @@
 /// to the platform.
 ///
 /// The [SemanticsNode] hierarchy represents the semantic structure of the UI
-/// and is used to by the platform-specific accessibility services.
+/// and is used by the platform-specific accessibility services.
 library semantics;
 
 export 'src/semantics/semantics.dart';
