refactor(rpc): miss stop PingPongLatencyTimer (backport cometbft#2792) (

cometbft#2795)

Closes cometbft#2771


---

#### PR checklist

- [ ] Tests written/updated
- [ ] Changelog entry added in `.changelog` (we use
[unclog](https://github.com/informalsystems/unclog) to manage our
changelog)
- [ ] Updated relevant documentation (`docs/` or `spec/`) and code
comments
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<hr>This is an automatic backport of pull request cometbft#2792 done by
[Mergify](https://mergify.com).

Co-authored-by: Khanh Hoa <[email protected]>

rpc/jsonrpc/client/ws_client.go

@@ -213,6 +213,7 @@ func (c *WSClient) Stop() error {
 	}
 	// only close user-facing channels when we can't write to them
 	c.wg.Wait()
+	c.PingPongLatencyTimer.Stop()
 	close(c.ResponsesCh)
 
 	return nil