fix(@angular/cli): require to run in a project if the help flag is present

[arturovt]

Closes: #16241

Currently, when running ng generate --help or any other command (e.g. ng add --help), it throws such exception:

An unhandled exception occurred: Unable to locate a workspace file for workspace path.
See "/tmp/ng-lBY5ie/angular-errors.log" for further details.

Angular CLI requires commands to be run in an Angular project only if there is no help flag.

This PR provides a small fix that removes condition allowing to always validate scope and throw:
The <command> command requires to be run in an Angular project

Except of unhandled exception.

Otherwise it would need to edit more code.

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