Reduce anki audio error level to log

<rikaitan.link>OGYwMDY4OGMxOWE4YzRmMjBiYzc3OGQ0ZWU0NDk3ZmNhYTJkM2RjYgo=</rikaitan.link>

ext/js/background/backend.js

@@ -2187,7 +2187,7 @@ export class Backend {
             const error = this._getAudioDownloadError(e);
             if (error !== null) { throw error; }
             // No audio
-            log.error(e);
+            log.logGenericError(e, 'log');
             return null;
         }