tweak: Increase warmup time for petclinic

Author: ddyurchenko

benchmark/load/petclinic/k6.js

@@ -7,12 +7,10 @@ export const options = {
   discardResponseBodies: true,
   scenarios: {
     [`load--petclinic--${__ENV.VARIANT}--warmup`]: {
-      executor: 'constant-arrival-rate',  // https://grafana.com/docs/k6/latest/using-k6/scenarios/executors/#all-executors
-      preAllocatedVUs: 5,
-      duration: '10s',
+      executor: 'constant-vus',  // https://grafana.com/docs/k6/latest/using-k6/scenarios/executors/#all-executors
+      vus: 5,
+      duration: '20s',
       gracefulStop: '2s',
-      timeUnit: '1s',
-      rate: 200,
     },
     [`load--petclinic--${__ENV.VARIANT}--high_load`]: {
       executor: 'constant-arrival-rate',