add missing valid_url_strict language string

Author: colethorsen

system/Language/en/Validation.php

@@ -57,6 +57,7 @@
     'valid_emails'          => 'The {field} field must contain all valid email addresses.',
     'valid_ip'              => 'The {field} field must contain a valid IP.',
     'valid_url'             => 'The {field} field must contain a valid URL.',
+    'valid_url_strict'      => 'The {field} field must contain a valid URL.',
     'valid_date'            => 'The {field} field must contain a valid date.',
 
     // Credit Cards