Fixed magnitude range

[Andr0id100]

For #76 .
Fixes the magnitude range for spectograms as (-200, 100). The range was chosen based on previously generated spectograms.

[Andr0id100]

Code quality action failure seems to be caused by a version issue with black.

Need to update tests before initiating the test action otherwise it would fail for save_spectogram

[valentina-s]

Thanks for the addition @Andr0id100. The plot_psd function is a general function, that could be used for different applications, so instead of fixing the bounds of the spectrogram there it is better to pass them as parameters and fix them in the workflow specification.