Typo in SSD documentation

[SHEscher]

Proposed documentation enhancement

Instead of "Spectro-Spatial Decomposition" it should be "spatio-spectral decomposition"

https://mne.tools/dev/auto_examples/decoding/ssd_spatial_filters.html#compute-spectro-spatial-decomposition-ssd-spatial-filters

[welcome]

Hello! 👋 Thanks for opening your first issue here! ❤️ We will try to get back to you soon. 🚴

[larsoner]

@SHEscher would you be up for making a PR to fix it?