Adjust to distributed deprecation about SchedulerPlugin's method signatures (#865)

Author: consideRatio

dask-gateway/dask_gateway/scheduler_preload.py

@@ -110,7 +110,7 @@ def __init__(self, service):
     def add_worker(self, scheduler, worker):
         self.service.worker_added(worker)
 
-    def remove_worker(self, scheduler, worker):
+    def remove_worker(self, scheduler, worker, **kwargs):
         self.service.worker_removed(worker)