message: Remove log-level-net-plugin option compeltely
  In my haste to fix net_plugin's gelf logging, I didn't remove the now defunct log-level-net-plugin config item
diff: @@ -2649,7 +2649,6 @@ namespace eosio {
  ( "peer-key", bpo::value<vector<string>>()->composing()->multitoken(), "Optional public key of peer allowed to connect. May be used multiple times.")
  ( "peer-private-key", boost::program_options::value<vector<string>>()->composing()->multitoken(),
  "Tuple of [PublicKey, WIF private key] (may specify multiple times)")
  - ( "log-level-net-plugin", bpo::value<string>()->default_value("info"), "Log level: one of 'all', 'debug', 'info', 'warn', 'error', or 'off'")
  ( "max-clients", bpo::value<int>()->default_value(def_max_clients), "Maximum number of clients from which connections are accepted, use 0 for no limit")
  ( "connection-cleanup-period", bpo::value<int>()->default_value(def_conn_retry_wait), "number of seconds to wait before cleaning up dead connections")
  ( "network-version-match", bpo::value<bool>()->default_value(false),
  