ExpansionPanelList elevation as double (#81813)

packages/flutter/lib/src/material/expansion_panel.dart

@@ -380,14 +380,8 @@ class ExpansionPanelList extends StatefulWidget {
 
   /// Defines elevation for the [ExpansionPanel] while it's expanded.
   ///
-  /// This uses [kElevationToShadow] to simulate shadows, it does not use
-  /// [Material]'s arbitrary elevation feature.
-  ///
-  /// The following values can be used to define the elevation: 0, 1, 2, 3, 4, 6,
-  /// 8, 9, 12, 16, 24.
-  ///
   /// By default, the value of elevation is 2.
-  final int elevation;
+  final double elevation;
 
   @override
   State<StatefulWidget> createState() => _ExpansionPanelListState();
@@ -560,7 +554,7 @@ class _ExpansionPanelListState extends State<ExpansionPanelList> {
     return MergeableMaterial(
       hasDividers: true,
       dividerColor: widget.dividerColor,
-      elevation: widget.elevation.toDouble(),
+      elevation: widget.elevation,
       children: items,
     );
   }

packages/flutter/test/material/expansion_panel_test.dart

@@ -20,7 +20,7 @@ class SimpleExpansionPanelListTestWidget extends StatefulWidget {
   final Key? secondPanelKey;
   final bool canTapOnHeader;
   final Color? dividerColor;
-  final int elevation;
+  final double elevation;
 
   /// If null, the default [ExpansionPanelList]'s expanded header padding value is applied via [defaultExpandedHeaderPadding]
   final EdgeInsets? expandedHeaderPadding;
@@ -1397,7 +1397,7 @@ void main() {
   });
 
   testWidgets('elevation is propagated properly to MergeableMaterial', (WidgetTester tester) async {
-    const int _elevation = 8;
+    const double _elevation = 8;
 
     // Test for ExpansionPanelList.
     await tester.pumpWidget(const MaterialApp(