[milo] fix typo.
[milo] fix typo.

Follow up on
https://crrev.com/c/1086516/3/milo/buildsource/buildbucket/builder.go#211

TBR=ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org

Change-Id: Id010f371b6ea5cf4cacc1dc6fc1442d39896705e
Reviewed-on: https://chromium-review.googlesource.com/1093524
Commit-Queue: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>
Reviewed-by: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>
Reviewed-by: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>

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