Add a missing dot in translations (laravel#5520)

Author: kapi2289

resources/lang/en/validation.php

@@ -90,7 +90,7 @@
         'string' => 'The :attribute must be at least :min characters.',
         'array' => 'The :attribute must have at least :min items.',
     ],
-    'multiple_of' => 'The :attribute must be a multiple of :value',
+    'multiple_of' => 'The :attribute must be a multiple of :value.',
     'not_in' => 'The selected :attribute is invalid.',
     'not_regex' => 'The :attribute format is invalid.',
     'numeric' => 'The :attribute must be a number.',