Fix publish_binary for Linux (#1915) Change back to `ubuntu1404` to not break existing users, which was changed to `ubuntu2004` in https://github.com/bazelbuild/continuous-integration/commit/c781266b1124d09ca1718a273bac9edf563a0975
See https://github.com/bazelbuild/continuous-integration/blob/master/buildkite/README.md