[macOS] Button's Font attributes arent setting when using color. (#971)

* [macOS] Button's font attributes werent working when TextColor was set.

* [macOS] Button's font attributes werent working when TextColor was set.

Xamarin.Forms.Platform.MacOS/Renderers/ButtonRenderer.cs

@@ -123,7 +123,7 @@ namespace Xamarin.Forms.Platform.MacOS
 			}
 			else
 			{
-				var textWithColor = new NSAttributedString(Element.Text ?? "", foregroundColor: color.ToNSColor( ), paragraphStyle: new NSMutableParagraphStyle( ) { Alignment = NSTextAlignment.Center });
+				var textWithColor = new NSAttributedString(Element.Text ?? "", font: Element.Font.ToNSFont(), foregroundColor: color.ToNSColor( ), paragraphStyle: new NSMutableParagraphStyle( ) { Alignment = NSTextAlignment.Center });
 				Control.AttributedTitle = textWithColor;
 			}
 		}