src/vs/platform/configuration/common/configurationRegistry.ts/ConfigurationRegistry/doDeregisterConfigurations
class ConfigurationRegistry:	private doDeregisterConfigurations(configurations: IConfigurationNode[]): string[] {
		const properties: string[] = [];
		const deregisterConfiguration = (configuration: IConfigurationNode) => {
			if (configuration.properties) {
				for (const key in configuration.properties) {
					properties.push(key);
					const property = this.configurationProperties[key];
					if (property?.policy?.name) {
						this.policyConfigurations.delete(property.policy.name);
					}
					delete this.configurationProperties[key];
					this.removeFromSchema(key, configuration.properties[key]);
				}
			}
			configuration.allOf?.forEach(node => deregisterConfiguration(node));
		};
		for (const configuration of configurations) {
			deregisterConfiguration(configuration);
			const index = this.configurationContributors.indexOf(configuration);
			if (index !== -1) {
				this.configurationContributors.splice(index, 1);
			}
		}
		return properties;
	}