MDEV-36714: Rows_log_event::write_data_header overallocates buffer size

Nothing is broken by this, but the function Rows_log_event::write_data_header slightly over-allocates its buf by 2 bytes. It allocates 10 (ROWS_HEADER_LEN_V2), but only 8 are ever written. This patch fixes the buf size to match what is written (i.e. ROWS_HEADER_LEN_V1, or 8 bytes). Reviewed By: ============ Kristian Nielsen <knielsen@knielsen-hq.org>

Author: bnestere

sql/log_event_server.cc

@@ -5514,7 +5514,7 @@ Rows_log_event::do_update_pos(rpl_group_info *rgi)
 
 bool Rows_log_event::write_data_header(Log_event_writer *writer)
 {
- uchar buf[ROWS_HEADER_LEN_V2]; // No need to init the buffer
+ uchar buf[ROWS_HEADER_LEN_V1]; // No need to init the buffer
  DBUG_ASSERT(m_table_id != UINT32_MAX);
  DBUG_EXECUTE_IF("old_row_based_repl_4_byte_map_id_master",
  {