[buildbucket] Serve 75% of prod ScheduleBuild requests
[buildbucket] Serve 75% of prod ScheduleBuild requests

Bug: 1042991
Change-Id: I8fff6dea5827c18a85eb8834bf0948f0da2b4d4f
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2964491
Reviewed-by: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@google.com>
Commit-Queue: smut <95deb7aa15d4c615299e47e7688551456568b1fb@google.com>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go