eth/filters: ensure API timeoutLoop terminates with event system (ethereum#31056)

Discovered from failing test introduced
ethereum#31033 . We should ensure
`timeoutLoop` terminates if the filter event system is terminated.

Author: jwasinger

eth/filters/api.go

@@ -90,7 +90,11 @@ func (api *FilterAPI) timeoutLoop(timeout time.Duration) {
 	ticker := time.NewTicker(timeout)
 	defer ticker.Stop()
 	for {
-		<-ticker.C
+		select {
+		case <-ticker.C:
+		case <-api.events.chainSub.Err():
+			return
+		}
 		api.filtersMu.Lock()
 		for id, f := range api.filters {
 			select {