Fix grammar reference in the definition of callback interfaces

They no longer use InterfaceRest.

Author: Ms2ger

index.bs

@@ -1425,7 +1425,10 @@ you can extend the {{WindowOrWorkerGlobalScope}} [=interface mixin=] using a [=p
 <h3 id="idl-callback-interfaces">Callback interfaces</h3>
 
 A <dfn id="dfn-callback-interface" export>callback interface</dfn> is a [=definition=] matching
-<emu-t>callback</emu-t> <emu-t>interface</emu-t> <emu-nt><a href="#prod-InterfaceRest">InterfaceRest</a></emu-nt>.
+<emu-t>callback</emu-t> <emu-t>interface</emu-t>
+<emu-t class="regex"><a href="#prod-identifier">identifier</a></emu-t> <emu-t>{</emu-t>
+<emu-nt><a href="#prod-CallbackInterfaceMembers">CallbackInterfaceMembers</a></emu-nt>
+<emu-t>}</emu-t> <emu-t>;</emu-t>.
 It can be implemented by any object, as described in [[#idl-objects]].
 
 Note: A [=callback interface=] is not an [=interface=]. The name and syntax are left over from