doc: add missing metadata for cluster.settings.cwd

PR-URL: #19569
Refs: #18399
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/cluster.md

@@ -731,6 +731,9 @@ values are `'rr'` and `'none'`.
 <!-- YAML
 added: v0.7.1
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/18399
+    description: The `cwd` option is supported now.
   - version: 8.2.0
     pr-url: https://github.com/nodejs/node/pull/14140
     description: The `inspectPort` option is supported now.