restore static block in jackson module

Author: diegomarquezp

google-http-client-jackson2/src/main/java/com/google/api/client/json/jackson2/JacksonFactory.java

@@ -60,11 +60,7 @@ public static JacksonFactory getDefaultInstance() {
 
   /** Holder for the result of {@link #getDefaultInstance()}. */
   static class InstanceHolder {
-    static final JacksonFactory INSTANCE;
-
-    static {
-      INSTANCE = new JacksonFactory();
-    }
+    static final JacksonFactory INSTANCE = new JacksonFactory();
   }
 
   @Override