Forward-fix a test that will break with an engine roll. (#133619)

See https://github.com/flutter/engine/pull/44705 where it fails a framework smoke test.

Partial work towards https://github.com/flutter/flutter/issues/112498.

packages/flutter/test/painting/text_style_test.dart

@@ -450,6 +450,13 @@ void main() {
   });
 
   test('backgroundColor', () {
+    // TODO(matanlurey): Remove when https://github.com/flutter/engine/pull/44705 rolls into the framework.
+    // Currently, dithering is disabled by default, but it's about to be flipped (enabled by default),
+    // and deprecated. This avoids #44705 causing a breakage in this test.
+    //
+    // ignore: deprecated_member_use
+    Paint.enableDithering = true;
+
     const TextStyle s1 = TextStyle();
     expect(s1.backgroundColor, isNull);
     expect(s1.toString(), 'TextStyle(<all styles inherited>)');
@@ -459,7 +466,16 @@ void main() {
     expect(s2.toString(), 'TextStyle(inherit: true, backgroundColor: Color(0xff00ff00))');
 
     final ui.TextStyle ts2 = s2.getTextStyle();
-    expect(ts2.toString(), contains('background: Paint(Color(0xff00ff00))'));
+
+    // TODO(matanlurey): Remove when https://github.com/flutter/flutter/issues/133698 is resolved.
+    // There are 5+ implementations of Paint, so we should either align the toString() or stop
+    // testing it, IMO.
+    if (kIsWeb) {
+      // The web implementation never includes "dither: ..." as a property.
+      expect(ts2.toString(), contains('background: Paint(Color(0xff00ff00))'));
+    } else {
+      expect(ts2.toString(), contains('background: Paint(Color(0xff00ff00); dither: true)'));
+    }
   });
 
   test('TextStyle background and backgroundColor combos', () {