Apply suggestion

Author: KodaiD

core/src/main/java/com/scalar/db/storage/objectstorage/cloudstorage/CloudStorageWrapper.java

@@ -41,11 +41,7 @@ public CloudStorageWrapper(CloudStorageConfig config) {
             .build()
             .getService();
     bucket = config.getBucket();
-    if (config.getParallelUploadBlockSizeInBytes().isPresent()) {
-      parallelUploadBlockSizeInBytes = config.getParallelUploadBlockSizeInBytes().get();
-    } else {
-      parallelUploadBlockSizeInBytes = null;
-    }
+    parallelUploadBlockSizeInBytes = config.getParallelUploadBlockSizeInBytes().orElse(null);
   }
 
   @VisibleForTesting