BirdNET doesn't use GPU

[sammlapp]

I have a Python environment with Tensorflow cuda installed (Pytorch CPU only) and I can use GPU with Perch inference. However, when loading and using the BirdNET model class, the GPU is not used.

A comparison of the BirdNET class in this repo with the Birdnet-Analayzer code (https://github.com/kahst/BirdNET-Analyzer/blob/main/model.py#L48) did not reveal any obvious differences. Perhaps the dependency requirements are different.