[Bugfix][Core] running queue index leakage exception (#26754)

Signed-off-by: CLFutureX <chenyongqyl@163.com>

vllm/v1/core/sched/scheduler.py

@@ -278,6 +278,7 @@ class Scheduler(SchedulerInterface):
                         token_budget += num_scheduled_tokens[preempted_req.request_id]
                         req_to_new_blocks.pop(preempted_req.request_id)
                         num_scheduled_tokens.pop(preempted_req.request_id)
+                        req_index -= 1
                 else:
                     preempted_req = self.running.pop()