For [the rule in the list](https://github.com/ClickHouse/ClickHouse/blob/82fc7375dd3ac4faae6c3b0db9f3a28fb2802d05/tests/config/top_level_domains/public_suffix_list.dat#L6430) `*.sch.uk` 

and domain like `www.something.sheffield.sch.uk`  the correct / expected result is `sheffield.sch.uk`

Example with python (correct)

```
-- pip install publicsuffix2
-- python3
>>> from publicsuffix2 import get_public_suffix
>>> get_public_suffix('www.something.sheffield.sch.uk')
'something.sheffield.sch.uk'
```

Same from clickhouse:
```
SELECT cutToFirstSignificantSubdomain('www.something.sheffield.sch.uk')

Query id: 9661461f-a393-43ea-97a1-47c0a8850515

┌─cutToFirstSignificantSubdomain('www.something.sheffield.sch.uk')─┐
│ sch.uk                                                           │
└──────────────────────────────────────────────────────────────────┘
```

/cc @azat 
while (pos < end)
        {
            if (lookup(pos + 1, end - pos - 1))
            {
                res_data += prev + 1 - begin;
                res_size = end - 1 - prev;
                return;
            }
            last_2_periods[1] = last_2_periods[0];
            last_2_periods[0] = pos;
            prev = pos;
            pos = find_first_symbols<'.'>(pos + 1, end);
        }
        
        if (!last_2_periods[0])
            return;
        
        if (!last_2_periods[1])
        {
            res_size = last_2_periods[0] - begin;
            return;
        }
        
        
        res_data += last_2_periods[1] + 1 - begin;
        res_size = last_2_periods[0] - last_2_periods[1] - 1;
    }
};
}