Fix typo.

packages/flutter/lib/src/widgets/ticker_provider.dart

@@ -73,7 +73,7 @@ class TickerMode extends InheritedWidget {
 /// This mixin only supports vending a single ticker. If you might have multiple
 /// [AnimationController] objects over the lifetime of the [State], use a full
 /// [TickerProviderStateMixin] instead.
-abstract class SingleTickerProviderStateMixin extends State<T> implements TickerProvider { // ignore: TYPE_ARGUMENT_NOT_MATCHING_BOUNDS, https://github.com/dart-lang/sdk/issues/25232
+abstract class SingleTickerProviderStateMixin extends State<dynamic> implements TickerProvider { // ignore: TYPE_ARGUMENT_NOT_MATCHING_BOUNDS, https://github.com/dart-lang/sdk/issues/25232
   // This class is intended to be used as a mixin, and should not be
   // extended directly.
   factory SingleTickerProviderStateMixin._() => null;