Use new API endpoint for scheduled job stats

Depends on:
- [ ] https://github.com/alphagov/notifications-api/pull/2984

app/notify_client/job_api_client.py

@@ -74,6 +74,11 @@ class JobApiClient(NotifyAdminAPIClient):
             reverse=True,
         )
 
+    def get_scheduled_job_stats(self, service_id):
+        return self.get(
+            url=f'/service/{service_id}/job/scheduled-job-stats'
+        )
+
     @cache.set('has_jobs-{service_id}')
     def has_jobs(self, service_id):
         return bool(self.get_jobs(service_id)['data'])