[embedlite-components] Remove clearance of general.useragent.override…

… user pref. Contributes to JB#52428

Clearing the general.useragent.override user pref was a temporary
addition intended to be removed on the next upgrade.

Reverts 8294975

jscomps/UserAgentOverrideHelper.js

@@ -37,18 +37,9 @@ UserAgentOverrideHelper.prototype = {
         Services.obs.addObserver(this, VIEW_DESKTOP_MODE_CHANGED, true);
         Services.obs.addObserver(this, VIEW_DESTROYED, true);
         Services.obs.addObserver(this, XPCOM_SHUTDOWN, false);
-        Services.prefs.addObserver(PREF_OVERRIDE, this, false);
         UserAgent.init();
         break;
       }
-      case "nsPref:changed": {
-        // Trigger by Preferences::InitializeUserPrefs after user prefs has been read.
-        if (aData === PREF_OVERRIDE) {
-            // Drop general.useragent.override from the in-memory prefs.
-            Services.prefs.clearUserPref(PREF_OVERRIDE);
-        }
-        break;
-      }
       case VIEW_CREATED: {
         UserAgent.addTabForWindow(aSubject)
         break;