Removed squidpy as docs dependency; using scanpy instead

[anushka255]

I realized that squidpy is not compatible with numpy>2.0, so removed it as a dependency. Squidpy was only used to visualize spots, so now I'm using the same functionality provided by scanpy.

[vineetbansal]

squidpy doesn't seem to declare that it needs numpy<2. Is there some minimal code/stacktrace that proves they're mistaken? If the problem is in a smaller 3rd party library we should pin that instead. I feel even if we don't use squidpy right now, its an important library in the domain and will be used sooner or later by someone using paste3.

[vineetbansal]

Great. Thanks!