remove pub from to_packet_batches_for_tests (#31056)

perf/src/packet.rs

@@ -224,7 +224,7 @@ pub fn to_packet_batches<T: Serialize>(items: &[T], chunk_size: usize) -> Vec<Pa
 }
 
 #[cfg(test)]
-pub fn to_packet_batches_for_tests<T: Serialize>(items: &[T]) -> Vec<PacketBatch> {
+fn to_packet_batches_for_tests<T: Serialize>(items: &[T]) -> Vec<PacketBatch> {
     to_packet_batches(items, NUM_PACKETS)
 }