Improve ThemeData.accentColor connection to secondary color (#31295)

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

@@ -486,6 +486,13 @@ class ThemeData extends Diagnosticable {
   final Color canvasColor;
 
   /// The foreground color for widgets (knobs, text, overscroll edge effect, etc).
+  ///
+  /// Accent color is also known as the secondary color.
+  ///
+  /// The theme's [colorScheme] property contains [ColorScheme.secondary], as
+  /// well as a color that contrasts well with the secondary color called
+  /// [ColorScheme.onSecondary]. It might be simpler to just configure an app's
+  /// visuals in terms of the theme's [colorScheme].
   final Color accentColor;
 
   /// The brightness of the [accentColor]. Used to determine the color of text