[Yaml] add missing indicator character

The comma was mentioned in the deprecation message, though it actually
was never checked before in the condition.

Author: xabbuh

Inline.php

@@ -463,7 +463,7 @@ private static function parseMapping($mapping, $flags, &$i = 0, $references = ar
                 break;
             }
 
-            if (!isset($mapping[$i + 1]) || !in_array($mapping[$i + 1], array(' ', '[', ']', '{', '}'), true)) {
+            if (!isset($mapping[$i + 1]) || !in_array($mapping[$i + 1], array(' ', ',', '[', ']', '{', '}'), true)) {
                 @trigger_error('Using a colon that is not followed by an indication character (i.e. " ", ",", "[", "]", "{", "}" is deprecated since version 3.2 and will throw a ParseException in 4.0.', E_USER_DEPRECATED);
             }