Add the missing label expires-after to the PR config

Signed-off-by: Rakshitha-Kamath <[email protected]>

Author: Rakshitha-Kamath

.tekton/snmp-notifier-pull-request.yaml renamed to .tekton/snmp-notifier-9-0-pull-request.yaml

@@ -24,6 +24,8 @@ spec:
     value: '{{revision}}'
   - name: output-image
     value: quay.io/rhceph-ci/snmp-notifier:on-pr-v9.0-{{revision}}
+  - name: image-expires-after
+    value: 5d
   - name: build-platforms
     value:
     - linux/x86_64