fix unstable case

tools/deploy/mysql_test/test_suite/static_engine/t/expr_sign.test

@@ -5,7 +5,6 @@
 
 --disable_abort_on_error
 --result_format 4
---explain_protocol 0
 
 connect (conn_admin, $OBMYSQL_MS0,admin,$OBMYSQL_PWD,oceanbase,$OBMYSQL_PORT);
 connection conn_admin;
@@ -79,7 +78,6 @@ insert into t2 values('GG1',3,'DD1',0.053,date'1974-03-19');
 
 --sleep 1
 
---explain_protocol 2
 select sign(null) from dual;
 
 let $cnt=22;