Simplify the previous patch a little

We can use BlockEntityType.getKey, rather than having to extend our
registry wrappers.

projects/common/src/test/java/dan200/computercraft/TestPlatformHelper.java

@@ -268,12 +268,6 @@ public class TestPlatformHelper extends AbstractComputerCraftAPI implements Plat
             return key;
         }
 
-        @Nullable
-        @Override
-        public ResourceLocation tryGetKey(T object) {
-            return registry.getKey(object);
-        }
-
         @Override
         public T get(ResourceLocation location) {
             var object = registry.get(location);