DRTVWR-447: Stop passing UpdaterServiceURL to leap updater.

In fact, mark UpdaterServiceURL as obsolete. (Consumers should consult
build_data.json.)

indra/newview/app_settings/settings.xml

@@ -13510,7 +13510,7 @@
     <key>UpdaterServiceURL</key>
     <map>
       <key>Comment</key>
-      <string>Default location for the updater service.</string>
+      <string>Obsolete; no longer used.</string>
       <key>Persist</key>
       <integer>0</integer>
       <key>Type</key>

indra/newview/llappviewer.cpp

@@ -1156,8 +1156,6 @@ bool LLAppViewer::init()
 	updater.args.add(LLVersionInfo::getChannel());
 	// testok
 	updater.args.add(stringize(gSavedSettings.getBOOL("UpdaterWillingToTest")));
-	// UpdaterServiceURL
-	updater.args.add(gSavedSettings.getString("UpdaterServiceURL"));
 	// ForceAddressSize
 	updater.args.add(stringize(gSavedSettings.getU32("ForceAddressSize")));