Add 'extra' test dep

python-subunit 1.4.3+ requires 'extras' otherwise an error
occures:
"'run --slowest' is not a stestr command."

Switch to using self-signed-certificates-operator as the
self signed functionality has been removed from
tls-certificates-operator charm *1

*1 2cb418cd2e

Change-Id: I47139a8d3203b4dc0953bc64491a9f58533d6a10

charms/ovn-relay-k8s/requirements.txt

@@ -10,4 +10,5 @@ jsonschema
 lightkube
 lightkube-models
 ops
+
 git+https://opendev.org/openstack/charm-ops-sunbeam#egg=ops_sunbeam

charms/ovn-relay-k8s/test-requirements.txt

@@ -8,3 +8,5 @@ coverage
 mock
 stestr
 ops
+# Subunit 1.4.3+ requires extras
+extras

charms/ovn-relay-k8s/tests/bundles/smoke.yaml

@@ -67,11 +67,10 @@ applications:
     resources:
       ovn-sb-db-server-image: ghcr.io/openstack-snaps/ovn-consolidated:23.03
   tls-operator:
-    charm: tls-certificates-operator
+    charm: self-signed-certificates
     channel: edge
     scale: 1
     options:
-      generate-self-signed-certificates: true
       ca-common-name: internal-ca
 
 relations: