2750: stop hiding Storage Manager UI #379

pref will be removed, 99% sure it was just a pref used internally to hide it from stable during testing in beta/nightly - see https://bugzilla.mozilla.org/show_bug.cgi?id=1428306. Makes zero sense to hide this new UI section since we will be turning SM on anyway (the section is important for end users to exist and be working esp thru QuotaManager and Storage v2 changes etc).

user.js

@@ -1430,13 +1430,11 @@ user_pref("dom.caches.enabled", false);
  * The API gives sites the ability to find out how much space they can use, how much
  * they are already using, and even control whether or not they need to be alerted
  * before the user agent disposes of site data in order to make room for other things.
- * [NOTE] This also controls the visibility of the "Options>Privacy & Security>Site Data"
- * section, which also requires Offline Cache (2730) enabled to function
+ * [NOTE] Requires Offline Cache (2730) enabled to function
  * [1] https://developer.mozilla.org/docs/Web/API/StorageManager
  * [2] https://developer.mozilla.org/docs/Web/API/Storage_API
  * [3] https://blog.mozilla.org/l10n/2017/03/07/firefox-l10n-report-aurora-54/ ***/
 user_pref("dom.storageManager.enabled", false); // (FF51+)
-user_pref("browser.storageManager.enabled", false); // (FF53+)
 
 /*** 2800: SHUTDOWN [SETUP]
      You should set the values to what suits you best. Be aware that the settings below clear