style: Declare appendJsonObject static.

Change-Id: I992c86866d1b8fd5212264a69c4d0845583a7db4
diff --git a/core/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/LogEntry.java b/core/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/LogEntry.java
index 8859cb6..5d4d9cf 100644
--- a/core/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/LogEntry.java
+++ b/core/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/LogEntry.java
@@ -212,7 +212,7 @@
     b.append("}");
   }
 
-  private void appendJsonObject(StringBuilder b, JsonValue value) {
+  private static void appendJsonObject(StringBuilder b, JsonValue value) {
     switch (value.getValueType()) {
       case ARRAY:
         b.append("[");