removeDocument method
Forgets documentId: flushes it, closes it, and drops it from the
catalog.
With the default catalog this deletes what the document holds — see BackendDocumentCatalog. Use releaseDocument to get a document out of memory and keep it on disk.
Implementation
@override
Future<void> removeDocument(String documentId) async {
await releaseDocument(documentId);
await _catalog.remove(documentId);
}