[Pkg-rust-maintainers] Bug#1069195: librust-prost-build-dev: FTBFS

[Peter Green]

> Unsatisfiable build-dependency on librust-heck-0.5+default-dev


There seems to be an error here. the version of librust-prost-dev in sid
(build-)depends on librust-heck-0.4+default-dev.

The version in experimental does depend on librust-heck-0.5+default-dev
as it's first choice, but that's fine because version 0.5 of rust-heck
is available in experimental.