Fix CCE in BrokerServerView

[navis]

Regression from #3935

Caused by: java.lang.ClassCastException: class io.druid.query.spec.DenseSegmentsSpec cannot be cast to class io.druid.query.spec.MultipleSpecificSegmentSpec (io.druid.query.spec.DenseSegmentsSpec and io.druid.query.spec.MultipleSpecificSegmentSpec are in unnamed module of loader 'app')
	at io.druid.client.BrokerServerView.toRunner(BrokerServerView.java:560) ~[druid-server-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.client.BrokerServerView.getQueryRunner(BrokerServerView.java:535) ~[druid-server-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.client.CachingClusteredClient$2.addSequencesFromServer(CachingClusteredClient.java:449) ~[druid-server-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.client.CachingClusteredClient$2.get(CachingClusteredClient.java:381) ~[druid-server-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.client.CachingClusteredClient.run(CachingClusteredClient.java:481) ~[druid-server-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.query.RetryQueryRunner.run(RetryQueryRunner.java:55) ~[druid-processing-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.query.UnionQueryRunner.run(UnionQueryRunner.java:50) ~[druid-processing-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.query.metadata.SegmentMetadataQueryQueryToolChest$3.doRun(SegmentMetadataQueryQueryToolChest.java:106) ~[druid-processing-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.query.BySegmentSkippingQueryRunner.run(BySegmentSkippingQueryRunner.java:48) ~[druid-processing-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.query.FinalizeResultsQueryRunner.run(FinalizeResultsQueryRunner.java:73) ~[druid-processing-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.query.PostProcessingOperators$1.run(PostProcessingOperators.java:53) ~[druid-processing-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.query.CPUTimeMetricQueryRunner.run(CPUTimeMetricQueryRunner.java:68) ~[druid-processing-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.query.BaseQuery.run(BaseQuery.java:377) ~[druid-processing-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]
	at io.druid.query.QueryRunners.run(QueryRunners.java:169) ~[druid-processing-2021.3-SNAPSHOT.jar:2021.3-SNAPSHOT]