deprecate broken method

Author: IThundxr

src/main/java/com/tterrag/registrate/builders/BlockBuilder.java

@@ -387,6 +387,7 @@ public BlockBuilder<T, P> clientExtension(NonNullSupplier<Supplier<IClientBlockE
      *            The client extension to register for this block
      * @return this {@link BlockBuilder}
      */
+    @Deprecated(forRemoval = true)
     public BlockBuilder<T, P> clientExtension(Function<T, NonNullSupplier<Supplier<IClientBlockExtensions>>> clientExtension) {
         if (this.clientExtensionFunc == null) {
             RegistrateDistExecutor.unsafeRunWhenOn(Dist.CLIENT, () -> this::registerClientExtension);

src/main/java/com/tterrag/registrate/builders/ItemBuilder.java

@@ -307,6 +307,7 @@ public ItemBuilder<T, P> clientExtension(NonNullSupplier<Supplier<IClientItemExt
         return this;
     }
 
+    @Deprecated(forRemoval = true)
     public ItemBuilder<T, P> clientExtension(Function<T, NonNullSupplier<Supplier<IClientItemExtensions>>> clientExtension) {
         if (this.clientExtensionFunc == null) {
             RegistrateDistExecutor.unsafeRunWhenOn(Dist.CLIENT, () -> this::registerClientExtension);