makes prototypeinheritance opt in

Content.Shared/Atmos/GasPrototype.cs

@@ -1,4 +1,4 @@
-#nullable enable
+#nullable enable
 using Robust.Shared.Prototypes;
 using Robust.Shared.Serialization.Manager.Attributes;
 using Robust.Shared.ViewVariables;
@@ -17,10 +17,6 @@ namespace Content.Shared.Atmos
         [field: DataField("id", required: true)]
         public string ID { get; } = default!;
 
-        [ViewVariables]
-        [field: DataField("parent")]
-        public string? Parent { get; }
-
         /// <summary>
         ///     Specific heat for gas.
         /// </summary>