notif: Enable autoCancel flag for summary notification

On Android 11 and lower, if autoCancel is not specified,
the summary notification may linger even after all child
notifications have been opened and cleared.

Author: rajveermalviya

lib/notifications/display.dart

@@ -158,6 +158,10 @@ class NotificationDisplayManager {
       inboxStyle: InboxStyle(
         // TODO(#570) Show organization name, not URL
         summaryText: data.realmUri.toString()),
+      // On Android 11 and lower, if autoCancel is not specified,
+      // the summary notification may linger even after all child
+      // notifications have been opened and cleared.
+      autoCancel: true,
     );
   }
 

test/notifications/display_test.dart

@@ -150,7 +150,7 @@ void main() {
             ..isGroupSummary.equals(true)
             ..inboxStyle.which((it) => it.isNotNull()
               ..summaryText.equals(data.realmUri.toString()))
-            ..autoCancel.isNull()
+            ..autoCancel.equals(true)
             ..contentIntent.isNull()
         ]);
     }