Update landscapeId to use constant 'LANDSCAPE_ID'

Author: VictorLeach96

README.md

@@ -68,7 +68,7 @@ public class Example {
         client.model().objects().list(
             ModelObjectsListRequest
                 .builder()
-                .landscapeId("landscapeId")
+                .landscapeId("LANDSCAPE_ID")
                 .versionId("latest")
                 .build()
         );
@@ -232,4 +232,4 @@ otherwise they would be overwritten upon the next generated release. Feel free t
 a proof of concept, but know that we will not be able to merge it as-is. We suggest opening
 an issue first to discuss with us!
 
-On the other hand, contributions to the README are always very welcome!
+On the other hand, contributions to the README are always very welcome!