openttd: 1.7.2 -> 1.8.0

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/openttd/versions.

These checks were done:

- built on NixOS
- ran ‘/nix/store/m11nsq51szvkzqnlsb3k7skqzh2781jp-openttd-1.8.0/bin/openttd -h’ got 0 exit code
- ran ‘/nix/store/m11nsq51szvkzqnlsb3k7skqzh2781jp-openttd-1.8.0/bin/openttd --help’ got 0 exit code
- ran ‘/nix/store/m11nsq51szvkzqnlsb3k7skqzh2781jp-openttd-1.8.0/bin/openttd help’ got 0 exit code
- ran ‘/nix/store/m11nsq51szvkzqnlsb3k7skqzh2781jp-openttd-1.8.0/bin/.openttd-wrapped -h’ got 0 exit code
- ran ‘/nix/store/m11nsq51szvkzqnlsb3k7skqzh2781jp-openttd-1.8.0/bin/.openttd-wrapped --help’ got 0 exit code
- ran ‘/nix/store/m11nsq51szvkzqnlsb3k7skqzh2781jp-openttd-1.8.0/bin/.openttd-wrapped help’ got 0 exit code
- found 1.8.0 with grep in /nix/store/m11nsq51szvkzqnlsb3k7skqzh2781jp-openttd-1.8.0
- directory tree listing: https://gist.github.com/8f8e59bc7bf394685911bd755a16c0a9