Update README.md for consistency

Update README.md specifically on the `sub_id` and `obj_id` to `sub_uri` and `obj_uri` respectively.

README.md

@@ -190,9 +190,9 @@ For each language and relation there are triples, that consists of an object, a
 Each instance has the following fields
 * "uuid": a unique identifier
 * "lineid": a identifier unique to mlama
-* "obj_id": knowledge graph id of the object
+* "obj_uri": knowledge graph id of the object
 * "obj_label": surface form of the object
-* "sub_id": knowledge graph id of the subject
+* "sub_uri": knowledge graph id of the subject
 * "sub_label": surface form of the subject
 * "template": template
 * "language": language code