93e0ed7 wrapped the curl_close call in a version check in main.

5.x.x still has this unguarded at https://github.com/jsonrainbow/json-schema/blob/5.x.x/src/JsonSchema/Uri/Retrievers/Curl.php#L54

As other PHP 8.5 changes are being made/backported as per https://github.com/jsonrainbow/json-schema/releases/tag/5.3.1 can we get this one done too?

I don't know if the whole linked commit above should be backported, or if we just want to make a partial backport (happy to do this).