Fixed typo in icon theme (#73247)

packages/flutter/lib/src/widgets/icon_theme_data.dart

@@ -26,7 +26,7 @@ class IconThemeData with Diagnosticable {
   /// is clamped between 0.0 and 1.0.
   const IconThemeData({this.color, double? opacity, this.size}) : _opacity = opacity;
 
-  /// Creates an icon them with some reasonable default values.
+  /// Creates an icon theme with some reasonable default values.
   ///
   /// The [color] is black, the [opacity] is 1.0, and the [size] is 24.0.
   const IconThemeData.fallback()