BUG: Fix conversion to datetime64[ns]

[snowman2]

E           TypeError: Cannot use .astype to convert from timezone-aware dtype to timezone-naive dtype. Use obj.tz_localize(None) or obj.tz_convert('UTC').tz_localize(None) instead.

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (e32d163) 97.21% compared to head (73d3d52) 97.21%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #143 +/- ## ======================================= Coverage 97.21% 97.21% ======================================= Files 14 14 Lines 431 431 ======================================= Hits 419 419 Misses 12 12 ``` | [Impacted Files](https://app.codecov.io/gh/corteva/geocube/pull/143?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=corteva) | Coverage Δ | | |---|---|---| | [geocube/vector\_to\_cube.py](https://app.codecov.io/gh/corteva/geocube/pull/143?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=corteva#diff-Z2VvY3ViZS92ZWN0b3JfdG9fY3ViZS5weQ==) | `100.00% <100.00%> (ø)` | |

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[snowman2]

Thanks @justingruca 👍