nixos/openssh: Drop deprecated locations

- The `ssh` client tool now disables the `~C` escape sequence by default. This can be re-enabled by setting `EnableEscapeCommandline yes`

- The `ssh` module does not read `/etc/ssh/ssh_known_hosts2` anymore since this location is [deprecated since 2001](https://marc.info/?l=openssh-unix-dev&m=100508718416162&w=2).

- The openssh module does not read `~/.ssh/authorized_keys2` anymore since this location is [deprecated since 2001](https://marc.info/?l=openssh-unix-dev&m=100508718416162&w=2).

- `podman` now uses the `netavark` network stack. Users will need to delete all of their local containers, images, volumes, etc, by running `podman system reset --force` once before upgrading their systems.

- `git-bug` has been updated to at least version 0.8.0, which includes backwards incompatible changes. The `git-bug-migration` package can be used to upgrade existing repositories.

      + (if h.publicKey != null then h.publicKey else readFile h.publicKeyFile)

    )) + "\n";

  knownHostsFiles = [ "/etc/ssh/ssh_known_hosts" "/etc/ssh/ssh_known_hosts2" ]

  knownHostsFiles = [ "/etc/ssh/ssh_known_hosts" ]

    ++ map pkgs.copyPathToStore cfg.knownHostsFiles;

in

        description = lib.mdDoc ''

          Files containing SSH host keys to set as global known hosts.

          `/etc/ssh/ssh_known_hosts` (which is

          generated by {option}`programs.ssh.knownHosts`) and

          `/etc/ssh/ssh_known_hosts2` are always

          included.

          generated by {option}`programs.ssh.knownHosts`) is

          always included.

        '';

        example = literalExpression ''

          [

    # https://github.com/NixOS/nixpkgs/pull/10155

    # https://github.com/NixOS/nixpkgs/pull/41745

    services.openssh.authorizedKeysFiles =

      [ "%h/.ssh/authorized_keys" "%h/.ssh/authorized_keys2" "/etc/ssh/authorized_keys.d/%u" ];

      [ "%h/.ssh/authorized_keys" "/etc/ssh/authorized_keys.d/%u" ];

    services.openssh.extraConfig = mkOrder 0

      ''