Update docker/.env.example

Co-authored-by: Bowen Liang <liang.bowen.123@qq.com>

docker/.env.example

@@ -142,7 +142,7 @@ CELERY_WORKER_CLASS=
 # it is recommended to set it to 360 to support a longer sse connection time.
 GUNICORN_TIMEOUT=360
 
-# Request keep-alive connection timeout. The default is 2.
+# The number of seconds to wait for requests on a Keep-Alive connection, default to 2
 GUNICORN_KEEP_ALIVE=2
 
 # The number of Celery workers. The default is 1, and can be set as needed.