Maintanence to comply with future Warnings

[nick-harder]

• drop python 3.10 and use python 3.11 and 3.12 instead
• update use of datetime to fit future depreciation of utcfromtimestamp()
• update "H" to "h" to comply with pandas

[codecov[bot]]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (3cd8bbe) 83.02% compared to head (a52c4dc) 77.95%.

Files	Patch %	Lines
assume/common/units_operator.py	33.33%	2 Missing :warning:
assume/common/mango_serializer.py	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #285 +/- ## ========================================== - Coverage 83.02% 77.95% -5.08% ========================================== Files 40 40 Lines 4536 4536 ========================================== - Hits 3766 3536 -230 - Misses 770 1000 +230 ``` | [Flag](https://app.codecov.io/gh/assume-framework/assume/pull/285/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=assume-framework) | Coverage Δ | | |---|---|---| | [pytest](https://app.codecov.io/gh/assume-framework/assume/pull/285/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=assume-framework) | `77.95% <66.66%> (-5.08%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=assume-framework#carryforward-flags-in-the-pull-request-comment) to find out more.

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