Makes cachedSplitResult transient in BigQuerySourceBase

Author: jkff

sdk/src/main/java/com/google/cloud/dataflow/sdk/io/BigQueryIO.java

@@ -1211,7 +1211,7 @@ private abstract static class BigQuerySourceBase extends BoundedSource<TableRow>
     protected final BigQueryServices bqServices;
     protected final ValueProvider<String> executingProject;
 
-    private List<BoundedSource<TableRow>> cachedSplitResult;
+    private transient List<BoundedSource<TableRow>> cachedSplitResult;
 
     private BigQuerySourceBase(
         String jobIdToken,