numpy 2.0 removal

[ericpre]

Use ruff check . --select NPY201 to find these.

For reference: https://numpy.org/devdocs/release/2.0.0-notes.html#numpy-2-0-python-api-removals.

Progress of the PR

• [x] Replace deprecated np.string_ by np.bytes_,
• [n/a] update docstring (if appropriate),
• [n/a] update user guide (if appropriate),
• [x] add a changelog entry in the upcoming_changes folder (see upcoming_changes/README.rst),
• [x] Check formatting of the changelog entry (and eventual user guide changes) in the docs/readthedocs.org:rosettasciio build of this PR (link in github checks)
• [n/a] add tests,
• [x] ready for review.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 86.36%. Comparing base (24fc42d) to head (fd8b1d5).

Files	Patch %	Lines
rsciio/utils/tools.py	0.00%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #238 +/- ## ======================================= Coverage 86.36% 86.36% ======================================= Files 83 83 Lines 10604 10604 Branches 2307 2307 ======================================= Hits 9158 9158 Misses 930 930 Partials 516 516 ```

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