Neutron: Do not set ovn_l3_mode

... because this option was deprecated[1] and has no effect with native
L3 support.

[1] 92952f016562cb89d1fd0ac320baff0786850aff

Change-Id: I788723aa45407735283dd7c52507d8b5c1ac8f7b

deployment/neutron/neutron-plugin-ml2-ovn.yaml

@@ -139,7 +139,6 @@ outputs:
             ovn::northbound::port: {get_param: OVNNorthboundServerPort}
             neutron::plugins::ml2::ovn::ovsdb_connection_timeout: {get_param: OVNDbConnectionTimeout}
             neutron::plugins::ml2::ovn::neutron_sync_mode: {get_param: OVNNeutronSyncMode}
-            neutron::plugins::ml2::ovn::ovn_l3_mode: true
             neutron::plugins::ml2::ovn::vif_type: {get_param: OVNVifType}
             neutron::plugins::ml2::ovn::ovn_metadata_enabled: {get_param: OVNMetadataEnabled}
             neutron::server::qos_notification_drivers: {get_param: OVNQosDriver}