allow registry manager to be overwritten

platforms/mixin-lifecycle/src/main/java/com/dfsek/terra/lifecycle/LifecyclePlatform.java

@@ -68,11 +68,8 @@ public abstract class LifecyclePlatform extends ModPlatform {
     }
     
     public static void addRegistryManager(DynamicRegistryManager in) {
-        if(DYNAMIC_REGISTRY_MANAGER.get() == null) {
         DYNAMIC_REGISTRY_MANAGER.set(Objects.requireNonNull(in));
     }
-        throw new IllegalStateException("Already set!");
-    }
     
     @Override
     protected Iterable<BaseAddon> platformAddon() {