Fixed a documentation typo in Control._drop_data() C#-example.

doc/classes/Control.xml

@@ -65,7 +65,7 @@
 				[csharp]
 				public override bool _CanDropData(Vector2 atPosition, Variant data)
 				{
-				    return data.VariantType == Variant.Type.Dictionary && dict.AsGodotDictionary().ContainsKey("color");
+				    return data.VariantType == Variant.Type.Dictionary && data.AsGodotDictionary().ContainsKey("color");
 				}
 
 				public override void _DropData(Vector2 atPosition, Variant data)