Add list around iterator in handle_missing_dep (#5285)

Co-authored-by: James Bourbeau <[email protected]>

distributed/worker.py

@@ -2554,7 +2554,7 @@ async def handle_missing_dep(self, *deps, **kwargs):
             if not deps:
                 return
 
-            for dep in deps:
+            for dep in list(deps):
                 if dep.suspicious_count > 5:
                     deps.remove(dep)
                     self.bad_dep(dep)