https://crates.io/crates/askama_axum says

askama_axum — deprecated

Integration crates like askama_axum were removed from askama 0.13.

Useful information can be found in our upgrade guide, and in our blog post.

This package does not seem to have any reverse dependencies in Debian, so
presumablly it should be removed. I'm filing this against the package in the
first instance though, in case anyone wants to object.