PHP API Ref: Fix external link CSS

Author: adriendupuis

tools/php_api_ref/.phpdoc/template/css/custom.css.twig

@@ -394,9 +394,9 @@ figcaption {
 }
 
 a.external:not(.card):after {
-    content: url(../images/open-in-new.svg);
+    content: url(../../../../images/open-in-new.svg);
     font-style: normal;
-    padding-left: 2px;
+    padding-left: 0px;
     position: relative;
     font-size: 11px;
     top: -5px;