CRM-18792, #378 - Catch-up on settings metadata

This is a follow-up to #12929.  In the interim between the writing and
merging of the PR, the version numbers changed.

settings/Core.setting.php

@@ -1076,7 +1076,7 @@ return [
       'callback' => 'call://themes/getAvailable',
     ),
     'default' => 'default',
-    'add' => '4.7',
+    'add' => '5.16',
     'title' => ts('Frontend Theme'),
     'is_domain' => 1,
     'is_contact' => 0,
@@ -1097,7 +1097,7 @@ return [
       'callback' => 'call://themes/getAvailable',
     ),
     'default' => 'default',
-    'add' => '4.7',
+    'add' => '5.16',
     'title' => ts('Backend Theme'),
     'is_domain' => 1,
     'is_contact' => 0,