refactor(ng-dev): use `instanceof` check for release precheck error
refactor(ng-dev): use `instanceof` check for release precheck error

Now that we share the same classes/code for the ng-dev CLI and exported
index entry-point, we should be able to use an `instanceof` check and
remove the workaround.

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