Fixes following numpy 2

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Project coverage is 83.50%. Comparing base (2bc6b38) to head (87df7a6).

Files	Patch %	Lines
pysteps/io/importers.py	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #365 +/- ## ======================================= Coverage 83.50% 83.50% ======================================= Files 159 159 Lines 12562 12564 +2 ======================================= + Hits 10490 10492 +2 Misses 2072 2072 ``` | [Flag](https://app.codecov.io/gh/pySTEPS/pysteps/pull/365/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS) | Coverage Δ | | |---|---|---| | [unit_tests](https://app.codecov.io/gh/pySTEPS/pysteps/pull/365/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pySTEPS) | `83.50% <85.71%> (+<0.01%)` | :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=pySTEPS#carryforward-flags-in-the-pull-request-comment) to find out more.

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