**How to reproduce**
Clickhouse server 20.13.1.5273
```
CREATE TABLE default.test
(
`key` UInt32,
`ts` DateTime CODEC(DoubleDelta, LZ4),
`db_time` DateTime DEFAULT now() COMMENT 'spout-ignore' CODEC(DoubleDelta, LZ4)
)
ENGINE = MergeTree
PARTITION BY toStartOfTenMinutes(db_time)
ORDER BY (key, ts)
TTL db_time + toIntervalHour(3)
SETTINGS index_granularity = 8192, merge_with_ttl_timeout = 3600, min_rows_for_compact_part = 1000000, min_bytes_for_compact_part = 200000000, in_memory_parts_enable_wal = 0;


INSERT INTO test(key, ts) SELECT number % 1000, now() + intDiv(number,1000) FROM numbers(500);

SELECT * FROM test;
500 rows in set. Elapsed: 0.003 sec.

DETACH TABLE test;

ATTACH TABLE test;

SELECT * FROM test;

0 rows in set. Elapsed: 0.002 sec.
```

**Expected behavior**
Clickhouse would flush parts on disk.
" because version column must be of an integer type or of type Date or DateTime"
            , ErrorCodes::ALTER_OF_COLUMN_IS_FORBIDDEN);
    auto which_new_type = WhichDataType(new_type);
    auto which_old_type = WhichDataType(old_type);
    
    if ((which_old_type.isInt() && !which_new_type.isInt())
        || (which_old_type.isUInt() && !which_new_type.isUInt())
        || (which_old_type.isDate() && !which_new_type.isDate())
        || (which_old_type.isDate32() && !which_new_type.isDate32())
        || (which_old_type.isDateTime() && !which_new_type.isDateTime())
        || (which_old_type.isFloat() && !which_new_type.isFloat()))
    {
        throw Exception("Cannot alter version column " + backQuoteIfNeed(column_name) +
            " from type " + old_type->getName() +
            " to type " + new_type->getName() + " because new type will change sort order of version column." +
            " The only possible conversion is expansion of the number of bytes of the current type."
            , ErrorCodes::ALTER_OF_COLUMN_IS_FORBIDDEN);
    }
    
    if (new_type->getSizeOfValueInMemory() < old_type->getSizeOfValueInMemory())
    {
        throw Exception("Cannot alter version column " + backQuoteIfNeed(column_name) +
            " from type " + old_type->getName() +
            " to type " + new_type->getName() + " because new type is smaller than current in the number of bytes." +
            " The only possible conversion is expansion of the number of bytes of the current type."
            , ErrorCodes::ALTER_OF_COLUMN_IS_FORBIDDEN);
    }
}
}
void MergeTreeData::checkAlterIsPossible(const AlterCommands & commands, ContextPtr local_context) const