fix: an issue causing timezone:false not to be respected

[pelletencate]

Groupdate has this delightful time_zone: false setting that allows you to group by date fields. I like using this in rollup as well, I have a table where I have a date field that the rollup is based on, but my app's TZ is usually somewhere in America. As a result, groupdate casts it to a time in the evening of the day before, and the whole rollup shifts one day backwards.

This PR intends to fix it by ignoring time zones if desired.

[ankane]

Thanks @pelletencate, great find and fix! Will push a new release shortly.