justinsb: bazel: remove deprecated stamp attribute from container building

JobBuild
b8f78e64
10-14 03:16
pull-kops-bazel-build 1184114761495744526 1183922997514211328 1183607595127017478 1183582177703497741
pull-kops-bazel-test 1184114761495744527 1183922997363216401 1183605832428818438 1183582177703497740
pull-kops-e2e-kubernetes-aws 1184104191518314500 1183922997363216395 1183912306422059008 1183757460133908480 1183737831302893568 1183607595127017472 1183582177703497739
pull-kops-verify-bazel 1184114761499938816 1183922997505822720 1183607595127017477 1183582177703497735
pull-kops-verify-boilerplate 1184114761495744523 1183922997363216397 1183607595127017475 1183582177703497734
pull-kops-verify-generated 1184114761495744524 1183922997363216402 1183607595122823176 1183582177703497732
pull-kops-verify-gofmt 1184114761499938817 1183922997480656896 1183607595127017474 1183582177703497738
pull-kops-verify-gomod 1184114761495744525 1183922997363216399 1183607595127017476 1183582177703497733
pull-kops-verify-govet 1184114761495744521 1183922997363216398 1183607595127017473 1183582177703497736
pull-kops-verify-packages 1184114761495744522 1183922997363216400 1183607595122823175 1183582177703497737