docs(DomCrawler): remove hint about html5-php library

html5-php is mandatory after symfony/symfony#44170

Author: kesselb

components/dom_crawler.rst

@@ -70,13 +70,6 @@ tree.
     isn't meant to dump content, you can see the "fixed" version of your HTML
     by :ref:`dumping it <component-dom-crawler-dumping>`.
 
-.. note::
-
-    If you need better support for HTML5 contents or want to get rid of the
-    inconsistencies of PHP's DOM extension, install the `html5-php library`_.
-    The DomCrawler component will use it automatically when the content has
-    an HTML5 doctype.
-
 Node Filtering
 ~~~~~~~~~~~~~~