Unpinning numpy version, addressing warnings

[astronomerritt]

Fixes #964.

• Unpinned Numpy version.
• Modified code to remove new warning for Numpy 2.0 (see below).
• Ensured fix also worked for older Numpy versions.

All tests ran successfully using Numpy v.2.0.1. However, the following new warning occurred:

tests/sorcha/test_PPLinkingFilter.py: 9 warnings
tests/sorcha/test_demo_end2end.py: 3 warnings
  /opt/miniconda3/envs/sorcha-numpy/lib/python3.10/site-packages/numpy/_core/records.py:634: DeprecationWarning: Data type alias 'a' was deprecated in NumPy 2.0. Use the 'S' alias instead.
    descr = sb.dtype(dtype)

This was a simple fix. MiniDifi uses Numpy record arrays in which the ssObjectID column was being typed as ssObjectId=f"a{nameLen}". Changed this to ssObjectId=f"S{nameLen}" in all places. This fix is backwards-compatible at least as far back as Numpy version 1.26.4 so it shouldn't break anyone's existing environments.

Review Checklist for Source Code Changes

• Does pip install still work?
• Have you written a unit test for any new functions?
• Do all the units tests run successfully?
• Does Sorcha run successfully on a test set of input files/databases?
• Have you used black on the files you have updated to confirm python programming style guide enforcement?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.78%. Comparing base (c661f54) to head (6f21950).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1004   +/-   ##
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  Coverage   80.78%   80.78%           
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  Files          69       69           
  Lines        3107     3107           
=======================================
  Hits         2510     2510           
  Misses        597      597           

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