Try using the below command:
ng update @angular/cli --migrate-only --from=1.7.4
It will perform the below
Updating karma configuration
Updating configuration
Removing old config file (.angular-cli.json)
Writing config file (angular.json)
Pls note that the above command should be run in the folder where you have file .angular-cli.json
and it will be then replaced by angular.json
.