refactor(ng-dev): do not print `undefined` when release prechecks fail
refactor(ng-dev): do not print `undefined` when release prechecks fail

We always print `undefined` upon release pre-check errors. The actual
pre-check error messaging is piped from the child process to
stdout/stderr, and therefore the the `spawn` utility-thrown error
is not necessary to be printed.

angular/dev-infra,angular/dev-infra,angular/dev-infra,angular/dev-infra