doc: fix YAML lint error on master

Refs: https://github.com/nodejs/node/runs/1275049330

PR-URL: #35709
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: Trott

doc/api/process.md

@@ -1916,6 +1916,7 @@ added: v11.12.0
 changes:
   - version:
      - REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/35654
     description: This API is no longer experimental.
 -->