removeAnnotation method
Implementation
Future<bool> removeAnnotation(int pageIndex, int objectNumber) async {
final UPdfDict? page = await mutablePage(pageIndex);
if (page == null) return false;
final Object? list = await document.resolve(page["Annots"]);
if (list is! List<Object?>) return false;
final List<Object?> next = list.where((Object? entry) => !(entry is UPdfRef && entry.number == objectNumber)).toList();
if (next.length == list.length) return false;
page["Annots"] = next;
put(objectNumber, null);
return true;
}