Update user agent to Firefox ESR 128

Author: TobiGr

extractor/src/test/java/org/schabi/newpipe/downloader/DownloaderTestImpl.java

@@ -18,8 +18,11 @@
 import okhttp3.ResponseBody;
 
 public final class DownloaderTestImpl extends Downloader {
+    /**
+     * Should be the latest Firefox ESR version.
+     */
     private static final String USER_AGENT
-            = "Mozilla/5.0 (Windows NT 10.0; rv:91.0) Gecko/20100101 Firefox/91.0";
+            = "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:128.0) Gecko/20100101 Firefox/128.0";
     private static DownloaderTestImpl instance;
     private final OkHttpClient client;