spec: bump once-ler

Change-Id: I19c034e891b777e3d54539ca1ca563db56ee0e94
Reviewed-on: https://gerrit.instructure.com/37392
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>