enhance: Remove current stats after RollStats action (#30391)

See also #27675

BloomFilterSet.current shall be reset after RollStats, otherwise it will
keep tracking whole segment data causing the false positive ratio larger
than expected.

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>

internal/datanode/metacache/bloom_filter_set.go

@@ -96,6 +96,7 @@ func (bfs *BloomFilterSet) Roll(newStats ...*storage.PrimaryKeyStats) {
 				MinPK:    stats.MinPk,
 			}
 		})...)
+		bfs.current = nil
 	}
 }