fix: wait for online key backup key to be cached on reset

Otherwise uploading the keys won't work, since the key backup is
"disabled".

lib/encryption/utils/bootstrap.dart

@@ -581,6 +581,17 @@ class Bootstrap {
       );
       Logs().v('Store the secret...');
       await newSsssKey?.store(megolmKey, base64.encode(privKey));
+      Logs().v('Wait for secret to come down sync');
+
+      if (!await encryption.keyManager.isCached()) {
+        await client.onSync.stream
+            .firstWhere((syncUpdate) =>
+                syncUpdate.accountData != null &&
+                syncUpdate.accountData!
+                    .any((accountData) => accountData.type == megolmKey))
+            .then((_) => Logs().v('New backup key was created'));
+      }
+
       Logs().v(
           'And finally set all megolm keys as needing to be uploaded again...');
       await client.database?.markInboundGroupSessionsAsNeedingUpload();