Revert "[Windows] Fix default corner radius on Button" (#10664)

* Revert "Fix default corner radius on Windows Button (#9515) Fixes #7128"

This reverts commit ed53643.

* add test

* remove unneeded class reference

* Move the test and check the native button

src/Core/src/Platform/Windows/ButtonExtensions.cs

@@ -50,7 +50,7 @@ public static void UpdateStrokeThickness(this Button platformButton, IButtonStro
 
 		public static void UpdateCornerRadius(this Button platformButton, IButtonStroke buttonStroke)
 		{
-			var radius = buttonStroke.CornerRadius > -1 ? buttonStroke.CornerRadius : 0;
+			var radius = buttonStroke.CornerRadius;
 
 			if (radius >= 0)
 				platformButton.Resources.SetValueForAllKey(CornerRadiusResourceKeys, WinUIHelpers.CreateCornerRadius(radius));

src/Core/tests/DeviceTests/Handlers/Button/ButtonHandlerTests.Windows.cs

@@ -38,6 +38,31 @@ public async Task CharacterSpacingInitializesCorrectly()
 			Assert.Equal(expectedValue, values.PlatformViewValue);
 		}
 
+		[Fact(DisplayName = "Rounded Maui Buttons Default Style")]
+		public async Task RoundedCornersMauiButtons()
+		{
+			var flatCornerRadius = 0;
+			var b = new Maui.Controls.Button();
+
+			var button = new ButtonStub()
+			{
+				// assign ButtonStub the default CornerRadius value of a Maui.Controls.Button
+				CornerRadius = b.CornerRadius
+			};
+
+			var values = await GetValueAsync(button, (handler) =>
+			{
+				return new
+				{
+					ViewValue = button.CornerRadius,
+					platformResources = handler.PlatformView.Resources
+				};
+			});
+
+			Assert.False(values.platformResources.ContainsKey("ControlCornerRadius"));
+			Assert.NotEqual(flatCornerRadius, values.ViewValue);
+		}
+
 		UI.Xaml.Controls.Button GetNativeButton(ButtonHandler buttonHandler) =>
 			buttonHandler.PlatformView;