doc: fix history information for node:diagnostics_channel

`node:diagnostics_channel` was backported to Node.js v14.17.0.

PR-URL: #46984
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>

Author: tlhunter

doc/api/diagnostics_channel.md

@@ -1,7 +1,9 @@
 # Diagnostics Channel
 
 <!-- YAML
-added: v15.1.0
+added:
+  - v15.1.0
+  - v14.17.0
 changes:
   - version: v19.2.0
     pr-url: https://github.com/nodejs/node/pull/45290