libobs: Remove DrawAlphaBlend technique

libobs/data/default.effect

@@ -62,13 +62,6 @@ float4 PSDrawNonlinearAlpha(VertInOut vert_in) : TARGET
 	return rgba;
 }
 
-float4 PSDrawAlphaBlend(VertInOut vert_in) : TARGET
-{
-	float4 rgba = image.Sample(def_sampler, vert_in.uv);
-	rgba.rgb *= rgba.a;
-	return rgba;
-}
-
 technique Draw
 {
 	pass
@@ -95,12 +88,3 @@ technique DrawNonlinearAlpha
 		pixel_shader  = PSDrawNonlinearAlpha(vert_in);
 	}
 }
-
-technique DrawAlphaBlend
-{
-	pass
-	{
-		vertex_shader = VSDefault(vert_in);
-		pixel_shader  = PSDrawAlphaBlend(vert_in);
-	}
-}