Make Nodes#nodeSchema default (for now)

Author: s1ck

core/src/main/java/org/neo4j/gds/core/loading/Nodes.java

@@ -34,7 +34,10 @@
 @ValueClass
 public interface Nodes {
 
-    NodeSchema schema();
+    @Value.Default
+    default NodeSchema schema() {
+        return NodeSchema.empty();
+    }
 
     IdMap idMap();