Move build-mechnical to 04:00 UTC

The goal being to ensure build-mechnical and the downstream build-node-image jobs
finish before we typically see content changed, which tends to be EMEA to US East
AM hours. In situations where we're hoping to pick up late changes this may cause
delays, if that becomes an issue I'd propose we consider adding a second run at
17:00 UTC (EDT 12:00 + 5hr), but ideally we'd limit that to only versions where we
hope to have rapid turn around. Those versions would be 9.6 today, then 9.6, 9.8,
and 10.2 starting approximately May 2026.

Author: sdodson

jobs/build-mechanical.Jenkinsfile

@@ -7,8 +7,8 @@ node {
 
 properties([
     pipelineTriggers([
-        // run every 24h at 10:00 UTC
-        cron("0 10 * * *")
+        // run every 24h at 04:00 UTC
+        cron("0 4 * * *")
     ]),
     buildDiscarder(logRotator(
         numToKeepStr: '100',