Update 4.1.0.md

Author: michaelklishin

release-notes/4.1.0.md

@@ -38,6 +38,10 @@ Clients that do override `frame_max` now must use values of 8192 bytes or greate
 We recommend using the default server value of `131072`: do not override the `frame_max`
 key in `rabbitmq.conf` and do not set it in the application code.
 
+[`amqplib`](https://github.com/amqp-node/amqplib/) is a popular client library that has been using
+a low `frame_max` default of `4096`. Its users must [upgrade to a compatible version](https://github.com/amqp-node/amqplib/pull/787)
+or explicitly use a higher `frame_max`.
+
 
 ### MQTT