remove labels on zoom in that aren't in scene

[davemcg]

For the meta plot in umap viz, labels are shown on the edge if not in zoomed-in scene. Very distracting.

[davemcg]

If I use scale_*_continous the points disappear. Not certain why.

Easy alternative is to stop using repel. But then some text labels overlap. Perhaps I should look into pre-computing the repelled label positions. This would also improve plotting time with labels by ~1 second.