bed_picks.ipynb is slow to build in CI

[thomasteisberg]

Our CI builds the docs notebooks. bed_picks.ipynb is a full five minutes slower than the next slowest notebook:

📖 Built notebooks/demo_notebook.ipynb in 2.9 min.
📖 Built notebooks/bed_picks.ipynb in 8.25 min.

I assume this is because the notebook fetches a large amount of BedMap data, but I haven't actually looked into it. We should make it faster for the sake of our CI pipelines while still demonstrating the same functionality.

[espg]

...this is down to 5.5 minutes in our latest build now.

Also, do we know if the timing is actually cumulative over all the notebooks? It says 9 pages build in 5.5 minutes, so I'm wondering if the CI timer is a running count for the notebooks as they render in the pipeline rather than a 'per notebook' timing on execution times. (If this is the case, then the markdown .md's are timed separately).

[thomasteisberg]

I don't think there's anything urgently needed here, but I figured it was a good first issue for someone interested in contributing. Jupyter Book 2 parallelizes notebook builds by default, but exactly what degree of parallelism and if this notebook is getting stuck waiting for others isn't clear to me.