modifications to accomodate numpy 2

[norinasunfospha]

🔬 Background

I want to use neuralprophet with numpy 2 since my other packages require it.

🔮 Key changes

I'm updating the package to use numpy 2

📋 Review Checklist

• I have performed a self-review of my own code.
• I have commented my code, added docstrings and data types to function definitions.
• I have added pytests to check whether my feature / fix works.

Please make sure to follow our best practices in the Contributing guidelines.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.17%. Comparing base (fa97742) to head (9ddacdf).
⚠️ Report is 25 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1700      +/-   ##
==========================================
- Coverage   88.27%   88.17%   -0.10%     
==========================================
  Files          41       44       +3     
  Lines        5364     5598     +234     
==========================================
+ Hits         4735     4936     +201     
- Misses        629      662      +33     

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