Remove "-fdmd-tx-dict-sel" flag.
It seems to offer choice for the sake of choice.
- It's badly documented. It's documentation just says "Use a special demand transformer for dictionary selectors." which gives users no idea if they want to use it or not.
- It's explicitly mentioned in zero packages on hackage.
- As far as I understand the logic I find it hard to come up with a reason why one would want to disable this.