Patch level dependency version specifiers should not by default translate to patch level greater than version constraints i.e. `(>= x.y.z)`

This behavior is of course semantically correct in the Rust ecosystem. However, in Debian, we often lack the manpower and time to follow every single package for their updates. It's common to have a slightly outdated version, e.g. 1.0.123 in Debian compared to 1.0.130 upstream, and it's OK most of the time. But debcargo generating the constraint verbatim means, to accommodate this, we have to either update all packages for those teeny tiny patch versions, or patch dependencies.

If there does exist the need to restrict a dependency to a minimum version, it can be achieved in some way by Breaks/Conflicts and the like, and we are going to update the dependency anyway.