Fix wrong error key in ReflectNodes (#1694)

pkl-core/src/main/java/org/pkl/core/stdlib/reflect/ReflectNodes.java

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,7 +32,10 @@ public final class ReflectNodes {
     @TruffleBoundary
     protected VmTyped eval(VmTyped self, VmTyped module) {
       if (!module.isModuleObject()) {
-        throw exceptionBuilder().evalError("expectedModule").withLocation(getArg1Node()).build();
+        throw exceptionBuilder()
+            .evalError("expectedModuleAsArgument")
+            .withLocation(getArg1Node())
+            .build();
       }
       return module.getModuleMirror();
     }