Fixed dartdoc related to SliverPrototypeExtentList and renamed the source file (#10174)

packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart

@@ -28,8 +28,6 @@ import 'sliver_multi_box_adaptor.dart';
 /// See also:
 ///
 ///  * [RenderSliverFixedExtentList], which has a configurable [itemExtent].
-///  * [RenderSliverPrototypeExtentList], which uses a prototype list item
-///    instead of a pixel value, to define the extent of each item.
 ///  * [RenderSliverFillViewport], which determines the [itemExtent] based on
 ///    [SliverConstraints.viewportMainAxisExtent].
 ///  * [RenderSliverFillRemaining], which determines the [itemExtent] based on
@@ -233,8 +231,6 @@ abstract class RenderSliverFixedExtentBoxAdaptor extends RenderSliverMultiBoxAda
 ///
 /// See also:
 ///
-///  * [RenderSliverPrototypeExtentList], which uses a prototype list item
-///    instead of a pixel value, to define the extent of each item.
 ///  * [RenderSliverList], which does not require its children to have the same
 ///    extent in the main axis.
 ///  * [RenderSliverFillViewport], which determines the [itemExtent] based on

packages/flutter/lib/src/widgets/sliver_prototype_item_list.dart → packages/flutter/lib/src/widgets/sliver_prototype_extent_list.dart

@@ -25,7 +25,7 @@ import 'sliver.dart';
 ///
 /// See also:
 ///
-///  * [SliverFixedExtentList], whose [itemExtent] is a pixel value.
+///  * [SliverFixedExtentList], whose itemExtent is a pixel value.
 ///  * [SliverList], which does not require its children to have the same
 ///    extent in the main axis.
 ///  * [SliverFillViewport], which sizes its children based on the

packages/flutter/lib/widgets.dart

@@ -72,7 +72,7 @@ export 'src/widgets/single_child_scroll_view.dart';
 export 'src/widgets/size_changed_layout_notifier.dart';
 export 'src/widgets/sliver.dart';
 export 'src/widgets/sliver_persistent_header.dart';
-export 'src/widgets/sliver_prototype_item_list.dart';
+export 'src/widgets/sliver_prototype_extent_list.dart';
 export 'src/widgets/status_transitions.dart';
 export 'src/widgets/table.dart';
 export 'src/widgets/text.dart';