doc: revise description of process.ppid

PR-URL: nodejs#35589
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/process.md

@@ -1739,7 +1739,8 @@ added:
 
 * {integer}
 
-The `process.ppid` property returns the PID of the current parent process.
+The `process.ppid` property returns the PID of the parent of the
+current process.
 
 ```js
 console.log(`The parent process is pid ${process.ppid}`);