Fix Firefox default prefs.

modules/desktop/files/etc/firefox-esr/prefs.js

@@ -11,10 +11,10 @@
  *
  * To make a manual change to preferences, you can visit the URL about:config
  */
-user_pref("browser.cache.disk.capacity", 1024);
-user_pref("browser.cache.disk.smart_size.enabled", false);
-user_pref("browser.cache.disk.smart_size.first_run", false);
-user_pref("browser.cache.disk.smart_size.use_old_max", false);
-user_pref("browser.download.useDownloadDir", false);
-user_pref("browser.startup.homepage", "http://ccc-ffm.de/getting-started/");
-user_pref("privacy.donottrackheader.enabled", true);
+defaultPref("browser.cache.disk.capacity", 1024);
+defaultPref("browser.cache.disk.smart_size.enabled", false);
+defaultPref("browser.cache.disk.smart_size.first_run", false);
+defaultPref("browser.cache.disk.smart_size.use_old_max", false);
+defaultPref("browser.download.useDownloadDir", false);
+defaultPref("browser.startup.homepage", "http://ccc-ffm.de/getting-started/");
+defaultPref("privacy.donottrackheader.enabled", true);