Reconfigured clean-expired-comped job to execute during morning UTC

refs https://ghost.slack.com/archives/C04MSE4MKJT/p1675948815531779

- running at a fixed hh:mm every day means a platform with a large number
  of Ghost sites will get hammered with DB requests when they all start
  up
- this reconfigures the cron to run at a random minute and second
  between 0am and 5am, which gives a 6 hour window

ghost/core/core/server/services/members/jobs/index.js

@@ -14,10 +14,12 @@ module.exports = {
         ) {
             // use a random seconds value to avoid spikes to external APIs on the minute
             const s = Math.floor(Math.random() * 60); // 0-59
+            const m = Math.floor(Math.random() * 60); // 0-59
+            const h = Math.floor(Math.random() * 6); // 0-5
 
-            // Run everyday at 12:05:X AM to clean all expired complimentary subscriptions
+            // Run everyday at {0-5}:XX:XX AM to clean all expired complimentary subscriptions
             jobsService.addJob({
-                at: `${s} 5 0 * * *`,
+                at: `${s} ${m} ${h} * * *`,
                 job: path.resolve(__dirname, 'clean-expired-comped.js'),
                 name: 'clean-expired-comped'
             });