Fix support for XML feeds with HTML entities (#7689)

fix https://github.com/FreshRSS/FreshRSS/issues/7687

https://github.com/FreshRSS/simplepie/pull/37
Upstream: https://github.com/simplepie/simplepie/pull/915

Partial revert of https://github.com/FreshRSS/FreshRSS/pull/7515

HTML entities are normally only allowed in XML when there is a DTD declaring them. SimplePie is even allowing Atom documents with undeclared HTML entities - which I am not sure is on purpose.

lib/composer.json

@@ -14,7 +14,7 @@
         "marienfressinaud/lib_opml": "0.5.1",
         "phpgt/cssxpath": "v1.3.0",
         "phpmailer/phpmailer": "6.10.0",
-        "simplepie/simplepie": "dev-freshrss#9a1c69be7d9dc2b766cef8697a2f1e88ab9a64e5"
+        "simplepie/simplepie": "dev-freshrss#f644950102ef4d4ab6e811db6ee9416d7151484a"
     },
     "config": {
         "sort-packages": true,