remove broken assert that is not needed and break account setup

it has been also removed from the original branch so no problem removing
it

Signed-off-by: Matthieu Gallien <matthieu.gallien@nextcloud.com>

src/libsync/abstractnetworkjob.cpp

@@ -149,8 +149,6 @@ void AbstractNetworkJob::adoptRequest(QNetworkReply *reply)
 
 QUrl AbstractNetworkJob::makeAccountUrl(const QString &relativePath) const
 {
-    // ensure we always used the remote folder
-    ASSERT(relativePath.startsWith(QLatin1Char('/')))
     return Utility::concatUrlPath(_account->url(), relativePath);
 }