Make SerializedTableHeader(numRows) public (#10949)

to be usable in different packages of spark-rapids to address 
NVIDIA/spark-rapids#5513

Signed-off-by: Gera Shegalov <gera@apache.org>

Authors:
  - Gera Shegalov (https://github.com/gerashegalov)

Approvers:
  - Jason Lowe (https://github.com/jlowe)

URL: #10949

java/src/main/java/ai/rapids/cudf/JCudfSerialization.java

@@ -1,6 +1,6 @@
 /*
  *
- *  Copyright (c) 2019-2021, NVIDIA CORPORATION.
+ *  Copyright (c) 2019-2022, NVIDIA CORPORATION.
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
@@ -108,7 +108,7 @@ public SerializedTableHeader(DataInputStream din) throws IOException {
     }
 
     /** Constructor for a row-count only table (no columns) */
-    SerializedTableHeader(int numRows) {
+    public SerializedTableHeader(int numRows) {
       this(new SerializedColumnHeader[0], numRows, 0);
     }