Upgrade ChromaDB to >=0.6.0 and fix broken tests

[smokestacklightnin]

This partially addresses #523 by updating the ChromaDB version to the latest 0.6.1 and patching particular test cases where ChromaDB's behavior differs from other databases.

[smokestacklightnin]

@pmeier For this test failure, should I typecast the return value of self._client.list_collections() to list[str], or should I change the type annotation of the return value of that function?

[pmeier]

Thanks William, LGTM. I took the liberty and fixed the remaining stuff myself. To answer your question: actually casting the object to the right type, i.e. list[str] is the best way to go here. The return type is Sequence[CollectionName] with isinstance(CollectionName, str). Both the custom container type as well as the custom string type are "implementation details" of Chroma that we don't need to expose to the Ragna user.

The last thing before merge is to add a warning to the docstring of Chroma explaining that the NE and and NOT_IN metadata filters also return sources that don't have the corresponding key set at all and this is different than all other builtin source storages.

[smokestacklightnin]

@pmeier I believe this PR is ready to be merged whenever you are ready

[pmeier]

Approving so you can self-merge after addressing the final comments and after #534 is merged and CI is green. Thanks William!