build: add missing `breakingChangeLabel` in ng-dev config
build: add missing `breakingChangeLabel` in ng-dev config

Currently, we are unable to merge breaking changes, because the label doesn't match the default value set in https://github.com/angular/angular/blob/1684b70b8830684deae4bae20c1e12aeddc4e1df/dev-infra/pr/merge/pull-request.ts#L23

geofffilippi/angular-cli,angular/angular-cli,Brocco/angular-cli,catull/angular-cli,angular/angular-cli,Brocco/angular-cli,catull/angular-cli,clydin/angular-cli,clydin/angular-cli,geofffilippi/angular-cli,geofffilippi/angular-cli,angular/angular-cli,catull/angular-cli,Brocco/angular-cli,clydin/angular-cli,angular/angular-cli,clydin/angular-cli,Brocco/angular-cli,geofffilippi/angular-cli,catull/angular-cli,Brocco/angular-cli