minisign: 0.7 -> 0.8

Semi-automatic update. These checks were performed:

- built on NixOS
- ran `/nix/store/3022qnvnd3j3zrz8qbyvv0izffbc17kj-minisign-0.8/bin/minisign -v` and found version 0.8
- ran `/nix/store/3022qnvnd3j3zrz8qbyvv0izffbc17kj-minisign-0.8/bin/minisign --version` and found version 0.8
- found 0.8 with grep in /nix/store/3022qnvnd3j3zrz8qbyvv0izffbc17kj-minisign-0.8
- found 0.8 in filename of file in /nix/store/3022qnvnd3j3zrz8qbyvv0izffbc17kj-minisign-0.8

cc "@joachifm"