Temporary memory leak in FutureImpl.executors (#8640)

* Temporary memory leak in `FutureImpl.executors`

* https://github.com/jenkinsci/jenkins-test-harness/pull/669 released

* Skip new test on Windows https://github.com/jenkinsci/jenkins/pull/8640#discussion_r1373797374

core/src/main/java/hudson/model/queue/FutureImpl.java

@@ -95,4 +95,8 @@ public final class FutureImpl extends AsyncFutureImpl<Executable> implements Que
     synchronized void addExecutor(@NonNull Executor executor) {
         this.executors.add(executor);
     }
+
+    synchronized void finished() {
+        executors.clear();
+    }
 }

core/src/main/java/hudson/model/queue/WorkUnitContext.java

@@ -190,6 +190,7 @@ public final class WorkUnitContext {
                         }
                     }
                 }
+                future.finished();
             }
         }
     }