extensions/references-view/src/references/model.ts/ReferencesModel/remove
class ReferencesModel:	remove(item: FileItem | ReferenceItem) {
		if (item instanceof FileItem) {
			del(this.items, item);
			this._onDidChange.fire(undefined);
		} else {
			del(item.file.references, item);
			if (item.file.references.length === 0) {
				del(this.items, item.file);
				this._onDidChange.fire(undefined);
			} else {
				this._onDidChange.fire(item.file);
			}
		}
	}