Remove installation of the ovs from the source in Devstack plugin

It is now moved to the Devstack repository so we don't need to keep it
in Neutron's Devstack plugin.

Depends-On: https://review.opendev.org/c/openstack/devstack/+/799621
Change-Id: Ic0d223a1da05a981077f2ec647df05c894d12790

devstack/plugin.sh

@@ -34,13 +34,6 @@ fi
 if [[ "$1" == "stack" ]]; then
     case "$2" in
         install)
-            if [[ "$NEUTRON_AGENT" == "openvswitch" ]] && \
-               [[ "$Q_BUILD_OVS_FROM_GIT" == "True" ]]; then
-                remove_ovs_packages
-                compile_ovs False /usr /var
-                load_conntrack_gre_module
-                start_new_ovs
-            fi
             ;;
         post-config)
             if is_service_enabled neutron-tag-ports-during-bulk-creation; then