Update copy on SSSS symmetric upgrade toast

Fixes https://github.com/vector-im/riot-web/issues/12881

src/components/views/toasts/SetupEncryptionToast.js

@@ -78,10 +78,11 @@ export default class SetupEncryptionToast extends React.PureComponent {
         switch (this.props.kind) {
             case 'set_up_encryption':
             case 'upgrade_encryption':
-            case 'upgrade_ssss':
                 return _t('Verify yourself & others to keep your chats safe');
             case 'verify_this_session':
                 return _t('Other users may not trust it');
+            case 'upgrade_ssss':
+                return _t('Update your secure storage');
         }
     }