expires vs expiration

It appears I have misunderstood the difference between `expires =>
time() + 3600` and `expiration => 3600` as I thought `expires` would
just set the expiration one time and not update for subsequent
requests. Per this discussion thread, that does not appear to be
correct:

https://github.com/mojolicious/mojo/discussions/1833

Thus I felt it best to just set the expiry period to 30 min and allow
that to reset on subsequent requests rather than reinvent the wheel

guestbook-ng.pl

@@ -43,14 +43,10 @@ under sub ($c) {
     unless ($c->session('counted')) {
         $c->counter->increment_visitor_count();
         $c->session(
-            expires => time() + 3600,
+            expiration => 1800,
             counted    => 1
             );
     }
-    # Delete this since I was supposed to be using 'expires' instead
-    # of 'expiration'; the difference is outlined here:
-    # https://docs.mojolicious.org/Mojolicious/Controller#session
-    delete $c->session->{'expiration'} if $c->session('expiration');
 
     $c->stash(status => 403) if $c->flash('error');