doc: improved joinDuplicateHeaders definition

PR-URL: nodejs#48859
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/http.md

@@ -3257,9 +3257,10 @@ changes:
   * `IncomingMessage` {http.IncomingMessage} Specifies the `IncomingMessage`
     class to be used. Useful for extending the original `IncomingMessage`.
     **Default:** `IncomingMessage`.
-  * `joinDuplicateHeaders` {boolean} It joins the field line values of multiple
-    headers in a request with `, ` instead of discarding the duplicates.
-    See [`message.headers`][] for more information.
+  * `joinDuplicateHeaders` {boolean} If set to `true`, this option allows
+    joining the field line values of multiple headers in a request with
+    a comma (`, `) instead of discarding the duplicates.
+    For more information, refer to [`message.headers`][].
     **Default:** `false`.
   * `keepAlive` {boolean} If set to `true`, it enables keep-alive functionality
     on the socket immediately after a new incoming connection is received,