listener: remove the todo about the drainning race problem (#16919)
listener: remove the todo about the drainning race problem (#16919)

Risk Level: low
Testing: n/a
Docs Changes: n/a
Release Notes: n/a
Signed-off-by: He Jie Xu <0fe0bd399dd39b6e2574442cf896a57f5611d8c7@intel.com>
envoyproxy/envoy,lyft/envoy,lyft/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,lyft/envoy,lyft/envoy,envoyproxy/envoy,envoyproxy/envoy