Remove trunk related functions from neutron devstack plugin

As was discussed on the neutron team meeting [1] this will be now
part of the Devstack repo so it's not needed in the neutron devstack
plugin anymore.

[1] https://meetings.opendev.org/meetings/networking/2021/networking.2021-10-05-14.00.log.html#l-156

Depends-On: https://review.opendev.org/c/openstack/devstack/+/812657

Change-Id: I04dacb43f244d71e1c5b74deb63b234b803033c9

devstack/lib/trunk

@@ -1,7 +0,0 @@
-function configure_trunk_service_plugin {
-    neutron_service_plugin_class_add "trunk"
-}
-
-function configure_trunk_extension {
-    configure_trunk_service_plugin
-}

devstack/plugin.sh

@@ -11,7 +11,6 @@ source $LIBDIR/ml2
 source $LIBDIR/network_segment_range
 source $LIBDIR/qos
 source $LIBDIR/segments
-source $LIBDIR/trunk
 source $LIBDIR/placement
 source $LIBDIR/log
 source $LIBDIR/fip_port_forwarding
@@ -58,9 +57,6 @@ if [[ "$1" == "stack" ]]; then
             if is_service_enabled q-qos neutron-qos; then
                 configure_qos
             fi
-            if is_service_enabled q-trunk neutron-trunk; then
-                configure_trunk_extension
-            fi
             if is_service_enabled q-placement neutron-placement; then
                 configure_placement_extension
             fi