reflection: Delete outdated paragraph in hasreturntype.xml (#5610)

Author: mmalferov

reference/reflection/reflectionfunctionabstract/hasreturntype.xml

@@ -38,7 +38,8 @@
 <![CDATA[
 <?php
 
-function to_int($param) : int {
+function to_int($param): int
+{
     return (int) $param;
 }
 
@@ -73,11 +74,6 @@ bool(false)
     </screen>
    </example>
   </para>
-  <para>
-   This is because many internal functions do not have types specified for their
-   parameters or return values. It is therefore best to avoid using this
-   method on built-in functions.
-  </para>
  </refsect1>
 
  <refsect1 role="seealso">