Incompatible with numpy>0.24

`np.int` and analogous expired their deprecation period and have been removed in Numpy 0.24.0: 
https://numpy.org/doc/stable/release/1.24.0-notes.html#expired-deprecations

This causes:
```python
import bsuite

# Output
AttributeError: module 'numpy' has no attribute 'int'
```