src/vs/workbench/contrib/welcomeGettingStarted/browser/gettingStartedService.ts/WalkthroughsService/deprogressStep
class WalkthroughsService:	deprogressStep(id: string) {
		delete this.stepProgress[id];
		this.memento.saveMemento();
		const step = this.getStep(id);
		this._onDidProgressStep.fire(this.getStepProgress(step));
	}