test: add decimal test back (#7349)

close #7334

tests/tidb-ci/fullstack-test-dt/issue_1425.test

@@ -24,7 +24,7 @@ func> wait_table test t
 
 # note: ref to https://github.com/pingcap/tiflash/issues/1682,
 # The precision of tiflash results is different from that of tidb, which is a compatibility issue
-# mysql> use test; set session tidb_isolation_read_engines='tiflash'; select * from t where value = 54/28;
+mysql> use test; set session tidb_isolation_read_engines='tiflash'; select * from t where value = 54/28;
 mysql> use test; set session tidb_isolation_read_engines='tiflash'; select * from t where value = c1/c2;
 +------+--------+------+------+
 | id   | value  | c1   | c2   |