Minor fixes numpy 2.0

[kkappler]

• [X] MTH5 notebooks failing on python >=3.9 due to:
  • AttributeError: np.float_ was removed in the NumPy 2.0 release. Use np.float64 instead
  • removed np.float_ reference, float64 was already there

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 85.06%. Comparing base (2d1f755) to head (d1e7bfa). Report is 32 commits behind head on main.

:exclamation: Current head d1e7bfa differs from pull request most recent head 8cf0644

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #213 +/- ## ========================================== + Coverage 85.02% 85.06% +0.04% ========================================== Files 270 270 Lines 20454 20480 +26 ========================================== + Hits 17391 17422 +31 + Misses 3063 3058 -5 ``` | [Flag](https://app.codecov.io/gh/kujaku11/mt_metadata/pull/213/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JP) | Coverage Δ | | |---|---|---| | [tests](https://app.codecov.io/gh/kujaku11/mt_metadata/pull/213/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JP) | `85.06% <100.00%> (+0.04%)` | :arrow_up: | 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=JP#carryforward-flags-in-the-pull-request-comment) to find out more.

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[kujaku11]

@kkappler I'll merge this once you confirm these changes work with MTH5.