Update documentation about accent color (flutter#116778)

Author: guidezpl

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

@@ -219,7 +219,7 @@ class CheckboxListTile extends StatelessWidget {
 
   /// The color to use when this checkbox is checked.
   ///
-  /// Defaults to accent color of the current [Theme].
+  /// Defaults to [ColorScheme.secondary] of the current [Theme].
   final Color? activeColor;
 
   /// The color to use for the check icon when this checkbox is checked.

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

@@ -245,7 +245,7 @@ class RadioListTile<T> extends StatelessWidget {
 
   /// The color to use when this radio button is selected.
   ///
-  /// Defaults to accent color of the current [Theme].
+  /// Defaults to [ColorScheme.secondary] of the current [Theme].
   final Color? activeColor;
 
   /// The primary content of the list tile.

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

@@ -266,7 +266,7 @@ class SwitchListTile extends StatelessWidget {
 
   /// The color to use when this switch is on.
   ///
-  /// Defaults to accent color of the current [Theme].
+  /// Defaults to [ColorScheme.secondary] of the current [Theme].
   final Color? activeColor;
 
   /// The color to use on the track when this switch is on.