rustc 1.55 was ignoring vaultwarden's `rust-version = 1.57`, causing
the build to succeed. rustc 1.56 was erroring out because it does not
ignore the minimum `rust-version`.
Patch out the `rust-version` because we do not really need 1.57;
rustc 1.56 with RUSTC_BOOTSTRAP=1 produces a working vaultwarden.
This fixes https://github.com/NixOS/nixpkgs/issues/146215
I tried to make this as non-breaking as possible, but it will still
break things slightly for people expecting certain file names in the
packages themselves.
