BUG: Cannot import neurodsp.timefrequency with latest SciPy 1.15

[larsoner]

scipy.signal.morlet has been removed so you get for example:

  File "/Applications/MNE-Python/1.9.0_0/.mne-python/lib/python3.12/site-packages/bycycle/features/shape.py", line 6, in <module>
    from neurodsp.timefrequency import amp_by_time
  File "/Applications/MNE-Python/1.9.0_0/.mne-python/lib/python3.12/site-packages/neurodsp/timefrequency/__init__.py", line 4, in <module>
    from .wavelets import compute_wavelet_transform, convolve_wavelet
  File "/Applications/MNE-Python/1.9.0_0/.mne-python/lib/python3.12/site-packages/neurodsp/timefrequency/wavelets.py", line 4, in <module>
    from scipy.signal import morlet
ImportError: cannot import name 'morlet' from 'scipy.signal' (/Applications/MNE-Python/1.9.0_0/.mne-python/lib/python3.12/site-packages/scipy/signal/__init__.py)
Error: Process completed with exit code 1.

Eventually you might want a good long-term solution, but for now I'd suggest perhaps just to vendor the old code. I can open a quick PR to do that if it would help.