Remove `angle` parameter from `linear-gradient` shader compilation

The angle is not used in the internal renderer, and not really needed for rendering. Further, the angle was not properly set when the gradient is directed at the corners. For these reasons, we simply remove the parameter.

Source/Core/DecoratorGradient.cpp

@@ -308,7 +308,6 @@ DecoratorDataHandle DecoratorLinearGradient::GenerateElementData(Element* elemen
 
 	CompiledShader shader = render_manager->CompileShader("linear-gradient",
 		Dictionary{
-			{"angle", Variant(angle)},
 			{"p0", Variant(gradient_shape.p0)},
 			{"p1", Variant(gradient_shape.p1)},
 			{"length", Variant(gradient_shape.length)},