ngspice: 26 -> 27

Semi-automatic update. These checks were done:

- built on NixOS
- Warning: no binary found that responded to help or version flags. (This warning appears even if the package isn't expected to have binaries.)
- found 27 with grep in /nix/store/73sh9hf5c9fjgh962pd1ac16kr8dvzxg-ngspice-27
- found 27 in filename of file in /nix/store/73sh9hf5c9fjgh962pd1ac16kr8dvzxg-ngspice-27