Fix unit tests. Remove default ctor.

src/Avalonia.Input/KeyGesture.cs

@@ -17,10 +17,6 @@ namespace Avalonia.Input
             { "+", Key.OemPlus }, { "-", Key.OemMinus }, { ".", Key.OemPeriod }
         };
 
-        public KeyGesture()
-        {
-        }
-
         [Obsolete("Use constructor taking KeyModifiers")]
         public KeyGesture(Key key, InputModifiers modifiers)
         {

tests/Avalonia.Controls.UnitTests/Utils/HotKeyManagerTests.cs

@@ -24,8 +24,8 @@ namespace Avalonia.Controls.UnitTests.Utils
                     .Bind<IWindowingPlatform>().ToConstant(new WindowingPlatformMock())
                     .Bind<IStyler>().ToConstant(styler.Object);
 
-                var gesture1 = new KeyGesture {Key = Key.A, Modifiers = InputModifiers.Control};
-                var gesture2 = new KeyGesture {Key = Key.B, Modifiers = InputModifiers.Control};
+                var gesture1 = new KeyGesture(Key.A, InputModifiers.Control);
+                var gesture2 = new KeyGesture(Key.B, InputModifiers.Control);
 
                 var tl = new Window();
                 var button = new Button();