Update migration-dsl.js

Sqlite driver with createtable causes the following error when using a primary key:
``` 
SQLITE_ERROR: table "x" has more than one primary key.
```
Generated sql:
```sql
CREATE TABLE `x` (`y` INTEGER PRIMARY KEY AUTOINCREMENT , PRIMARY KEY (`y`))
```
i dont think that this is the best solution for the problem but at least it works :)