prow: sinker/horologium: revert flag changes for starter.yaml
prow: sinker/horologium: revert flag changes for starter.yaml

This should have been done as part of
5de290cec3b7162be40639f3bafb74306dcbd11a. Without this, both sinker and
horologium go into CrashLoopBackOff because the flag is unrecognized.

cblecker/test-infra,dims/test-infra,shyamjvs/test-infra,monopole/test-infra,krzyzacy/test-infra,dims/test-infra,shyamjvs/test-infra,monopole/test-infra,dims/test-infra,monopole/test-infra,kubernetes/test-infra,lavalamp/test-infra,cblecker/test-infra,jessfraz/test-infra,pwittrock/test-infra,cjwagner/test-infra,brahmaroutu/test-infra,krzyzacy/test-infra,lavalamp/test-infra,shyamjvs/test-infra,krzyzacy/test-infra,jlowdermilk/test-infra,brahmaroutu/test-infra,dims/test-infra,BenTheElder/test-infra,lavalamp/test-infra,pwittrock/test-infra,cblecker/test-infra,michelle192837/test-infra,jlowdermilk/test-infra,jlowdermilk/test-infra,kubernetes/test-infra,cblecker/test-infra,fejta/test-infra,krzyzacy/test-infra,michelle192837/test-infra,lavalamp/test-infra,jlowdermilk/test-infra,ixdy/kubernetes-test-infra,kubernetes/test-infra,pwittrock/test-infra,jessfraz/test-infra,fejta/test-infra,kubernetes/test-infra,monopole/test-infra,brahmaroutu/test-infra,michelle192837/test-infra,ixdy/kubernetes-test-infra,shyamjvs/test-infra,brahmaroutu/test-infra,fejta/test-infra,michelle192837/test-infra,brahmaroutu/test-infra,BenTheElder/test-infra,cjwagner/test-infra,michelle192837/test-infra,BenTheElder/test-infra,fejta/test-infra,lavalamp/test-infra,BenTheElder/test-infra,cblecker/test-infra,ixdy/kubernetes-test-infra,BenTheElder/test-infra,pwittrock/test-infra,kubernetes/test-infra,ixdy/kubernetes-test-infra,jessfraz/test-infra,pwittrock/test-infra,fejta/test-infra,michelle192837/test-infra,BenTheElder/test-infra,monopole/test-infra,shyamjvs/test-infra,monopole/test-infra,dims/test-infra,jessfraz/test-infra,lavalamp/test-infra,shyamjvs/test-infra,cjwagner/test-infra,brahmaroutu/test-infra,cblecker/test-infra,cjwagner/test-infra,dims/test-infra,jessfraz/test-infra,cjwagner/test-infra,krzyzacy/test-infra,jlowdermilk/test-infra,ixdy/kubernetes-test-infra,kubernetes/test-infra,fejta/test-infra,krzyzacy/test-infra,jessfraz/test-infra,jlowdermilk/test-infra,cjwagner/test-infra