API/DOC: adjustments for v2025.12 of the standard

A few changes in [the latest version of the standard](https://data-apis.org/array-api/draft/changelog.html#v2025-12) are related to functions in this library, e.g. `expand_dims`, `isin`, `broadcast_shapes`. We should update documentation to reflect any new additions and consider a longer-term plan for handling API duplication.