Switch to OVS/OVN LTS branches

As discussed in Epoxy PTG[1] switching jobs to run
with latest OVS/OVN LTS branches.
Ubuntu noble and CentOS 9-stream also including these
LTS versions.

[1] https://etherpad.opendev.org/p/oct2024-ptg-neutron

Change-Id: Iecb33628641cd33b6e46d09759e3180cc0bd55e9
diff --git a/lib/neutron_plugins/ovs_source b/lib/neutron_plugins/ovs_source
index 75e7d7c..6b6f531 100644
--- a/lib/neutron_plugins/ovs_source
+++ b/lib/neutron_plugins/ovs_source
@@ -20,7 +20,7 @@
 OVS_REPO=${OVS_REPO:-https://github.com/openvswitch/ovs.git}
 OVS_REPO_NAME=$(basename ${OVS_REPO} | cut -f1 -d'.')
 OVS_REPO_NAME=${OVS_REPO_NAME:-ovs}
-OVS_BRANCH=${OVS_BRANCH:-0047ca3a0290f1ef954f2c76b31477cf4b9755f5}
+OVS_BRANCH=${OVS_BRANCH:-branch-3.3}
 
 # Functions