Skip setting language field on discovery file

Author: testower

gbfs-validator-java-api/src/main/java/org/entur/gbfs/validator/api/handler/ValidateApiDelegateHandler.java

@@ -120,7 +120,9 @@ private List<GbfsFile> mapFiles(Map<String, FileValidationResult> files, @Nullab
             //file.setUrl(); // TODO must be carried from loader
             file.setSchema(fileValidationResult.schema());
             file.setVersion(fileValidationResult.version());
-            file.setLanguage(JsonNullable.of(language));
+
+            // The discovery file itself has no language, and is listed once per system
+            file.setLanguage(!fileName.equals("gbfs") ? JsonNullable.of(language) : null);
             file.setErrors(mapFileErrors(fileValidationResult.errors()));
             return file;
         }).toList();