fix: 解决 spotbugs 报 SE_BAD_FIELD 错误

Author: liuweiGL

src/main/java/io/jenkins/plugins/DingTalkStep.java

@@ -210,7 +210,8 @@ public StepExecution start(StepContext context) throws Exception {
 
   private static class DingTalkStepExecution extends StepExecution {
 
-    private final DingTalkStep step;
+    private static final long serialVersionUID = 1L;
+    private final transient DingTalkStep step;
 
     private DingTalkStepExecution(DingTalkStep step, StepContext context) {
       super(context);