port changes from fec9800

Author: adutra

core/src/main/java/org/apache/iceberg/rest/requests/RemoteSignRequestParser.java

@@ -120,8 +120,8 @@ public static Map<String, List<String>> headersFromJson(String property, JsonNod
     Map<String, List<String>> headers = Maps.newHashMap();
     JsonNode headersNode = JsonUtil.get(property, json);
     headersNode
-        .fields()
-        .forEachRemaining(
+        .properties()
+        .forEach(
             entry -> {
               String key = entry.getKey();
               List<String> values = Arrays.asList(JsonUtil.getStringArray(entry.getValue()));