Updated code to be compatible with php-etl/pipeline-contracts:0.5

Author: gplanchat

src/State.php

@@ -9,7 +9,6 @@
 
 final class State implements StepStateInterface
 {
-    private array $steps = [];
     private int $acceptMetric = 0;
     private int $rejectMetric = 0;
     private int $errorMetric = 0;

src/StateManager.php

@@ -10,7 +10,6 @@
 class StateManager
 {
     /** @var list<State> */
-    private array $states = [];
     private array $steps = [];
     private array $tearedDown = [];
     private int $messageCount = 0;