Updated AlertDialog content doc (#26613)

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

@@ -242,9 +242,10 @@ class AlertDialog extends StatelessWidget {
   /// The (optional) content of the dialog is displayed in the center of the
   /// dialog in a lighter font.
   ///
-  /// Typically, this is a [ListView] containing the contents of the dialog.
-  /// Using a [ListView] ensures that the contents can scroll if they are too
-  /// big to fit on the display.
+  /// Typically this is a [SingleChildScrollView] that contains the dialog's
+  /// message. As noted in the [AlertDialog] documentation, it's important
+  /// to use a [SingleChildScrollView] if there's any risk that the content
+  /// will not fit.
   final Widget content;
 
   /// Padding around the content.