update DebugScope error message (#1688)

Make the scope id in error messages consistent between the detached-with-error and not-detached cases,
by using spl_object_id($this) in the latter to match the former.

Author: brettmc

src/Context/DebugScope.php

@@ -78,7 +78,7 @@ public function __destruct()
 
             trigger_error(sprintf(
                 'Scope: missing call to Scope::detach() for scope #%d, created %s',
-                spl_object_id($this->scope),
+                spl_object_id($this),
                 self::formatBacktrace($this->createdAt),
             ));
         }