Support anndata 12

[sophiamaedler]

implements fix suggested by @machth in #317

• unpins anndata and spatialdata dependencies
• fixes issues resulting in incompatibility with anndata 0.12

[Zethson]

@sophiamaedler I'd love to have this PR merged with a release. Would you need any support or help here? Maybe you already know why the tests failed but if not, we can dig into it.

Thank you!

[sophiamaedler]

@sophiamaedler I'd love to have this PR merged with a release. Would you need any support or help here? Maybe you already know why the tests failed but if not, we can dig into it.

Thank you!

Anndata unpin works already, but the spatialdata one is the issue.

The tests are failing because some of our spatial data operations are no longer functional.

I dug into this a bit and tried to find a new correct way to do it, but haven't found a solution as of yet.

I'd have to go back to find the specifics, but it fundamentally related to this type of support missing in spatialdata: scverse/spatialdata#906

I originally hacked a way of getting a similar result which we required for our application, but
it no longer works with the new spatial data release.

[Zethson]

Ahh, I see. Could you point me to your hacked version, please?