Remove deprecated (and useless) function finfo_close

src/MD_STD.php

@@ -741,7 +741,6 @@ public static function mime_content_type(string $filepath):string {
         if (!($mime_type = finfo_file($finfo, $filepath))) {
             throw new MDWrongFileType("Cannot get mime type of file: " . basename($filepath));
         }
-        \finfo_close($finfo);
 
         return $mime_type;