#[\Override]: document restriction on __construct() (#4738)

Co-authored-by: Tim Düsterhus <[email protected]>

Author: DanielEScherzer

language/predefined/attributes/override.xml

@@ -17,6 +17,11 @@
     in an implemented interface a compile-time error will be
     emitted.
    </simpara>
+   <simpara>
+    The attribute cannot be used on the
+    <link linkend="object.construct">__construct()</link>
+    method, which is exempt from signature checks.
+   </simpara>
   </section>
 
   <section xml:id="override.synopsis">