message: update changeset to be 'patch' change
  Per code review feedback:
diff: ---
  -'@backstage/plugin-splunk-on-call': minor
  +'@backstage/plugin-splunk-on-call': patch
  ---
  Add Splunk On-Call plugin support for a `splunk.com/on-call-routing-key` annotation. If the `splunk.com/on-call-routing-key` is provided, the plugin displays a Splunk On-Call card for each of the teams associated with the routing key.
  