[DomCrawler] Clarify the value returned by getPhpFiles()
[DomCrawler] Clarify the value returned by getPhpFiles()

The comment was previously suggesting the returned value is similar to the one stored in $_FILES, while it is more similar to the way PHP stores submitted form values. It is actually more convenient to have it this way, so rather then changing the returned value (which would break BC), it is better to clarify the comment.

symfony/dom-crawler,symfony/dom-crawler,symfony/DomCrawler,symfony/DomCrawler