docs: add more description for max_connection_duration in timeout faqs (#18193)

This PR adds some more description around max_connection_duration in the Timeout FAQs.

Commit Message: add more description for max_connection_duration in timeout faqs.
Additional Description: -
Risk Level: N/A
Testing: N/A
Docs Changes: Added some more description around max_connection_duration in the Timeout FAQs.
Release Notes: N/A
Platform Specific Features: N/A

Signed-off-by: Rohit Agrawal <rohit.agrawal@databricks.com>

Mirrored from https://github.com/envoyproxy/envoy @ 2e8efdefef86f7749aee3ca30d0752218a07ca8a

envoy/config/core/v3/protocol.proto

@@ -155,10 +155,11 @@ message HttpProtocolOptions {
 
   // The maximum duration of a connection. The duration is defined as a period since a connection
   // was established. If not set, there is no max duration. When max_connection_duration is reached
-  // the connection will be closed. Drain sequence will occur prior to closing the connection if
-  // if's applicable. See :ref:`drain_timeout
+  // and if there are no active streams, the connection will be closed. If there are any active streams,
+  // the drain sequence will kick-in, and the connection will be force-closed after the drain period.
+  // See :ref:`drain_timeout
   // <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.drain_timeout>`.
-  // Note: not implemented for upstream connections.
+  // Note: This feature is not yet implemented for the upstream connections.
   google.protobuf.Duration max_connection_duration = 3;
 
   // The maximum number of headers. If unconfigured, the default