doc correction for `idle_timeout`

[cruvie]

https://www.envoyproxy.io/docs/envoy/latest/configuration/best_practices/edge

                route:
                  cluster: service_foo
                  idle_timeout: 15s  # must be disabled for long-lived and streaming requests

the idle_timeout should be replaced with timeout

the idle_timeout will cause grpc-web server side stream failed!

[wbpcode]

You are right. Thanks for catching it. Actually, there are both timeout and idle_timeout. The timeout should be disabled for long live stream. And the idle_timeout could be optionally set based on the stream characteristcs.

[agrawroh]

Closing this as @wbpcode already merged the doc fix.