[release] Also split the onlyPackages param (#32777)

I missed this the last time.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/32777).
* #32778
* __->__ #32777

Author: poteto

scripts/release/prepare-release-from-npm-commands/parse-params.js

@@ -56,6 +56,7 @@ module.exports = () => {
   const params = commandLineArgs(paramDefinitions);
 
   splitCommaParams(params.skipPackages);
+  splitCommaParams(params.onlyPackages);
 
   return params;
 };

scripts/release/publish-commands/parse-params.js

@@ -49,6 +49,7 @@ const paramDefinitions = [
 module.exports = () => {
   const params = commandLineArgs(paramDefinitions);
   splitCommaParams(params.skipPackages);
+  splitCommaParams(params.onlyPackages);
   splitCommaParams(params.tags);
   params.tags.forEach(tag => {
     switch (tag) {