ci: reduce update-builder workflow schedule from hourly to every 4 hours #3563

Problem

The update-builder.yaml workflow runs on an hourly cron schedule (0 * * * *), while all other update workflows (update-quarkus-platform.yaml, update-springboot-platform.yaml, update-python-platform.yaml) run every 4 hours or daily.

The builder image is published by an external team and does not change hourly. Running this workflow 24 times/day instead of 6 wastes approximately 18 runner-hours/day for no practical benefit.

Fix

Change the cron schedule in .github/workflows/update-builder.yaml from 0 * * * * to 0 */4 * * * to match the cadence of other update workflows.

Affected File

.github/workflows/update-builder.yaml