change transcode downloads to ask by default

lib/models/finamp_models.dart

@@ -89,7 +89,7 @@ const _swipeInsertQueueNext = true;
 const _defaultLoopMode = FinampLoopMode.none;
 const _defaultPlaybackSpeed = 1.0;
 const _autoLoadLastQueueOnStartup = true;
-const _shouldTranscodeDownloadsDefault = TranscodeDownloadsSetting.never;
+const _shouldTranscodeDownloadsDefault = TranscodeDownloadsSetting.ask;
 const _shouldRedownloadTranscodesDefault = false;
 const _defaultResyncOnStartup = true;
 const _fixedGridTileSizeDefault = 150;