nixos/mobilizon: change psql socket dir to none symlinked directory

  dbUser = if repoSettings.username != null then repoSettings.username else "mobilizon";

  postgresql = config.services.postgresql.package;

  postgresqlSocketDir = "/var/run/postgresql";

  postgresqlSocketDir = "/run/postgresql";

  secretEnvFile = "/var/lib/mobilizon/secret-env.sh";

in