fix: split on comma

[shetzel]

What does this PR do?

The code was splitting on a space char when it needed to be a comma.

What issues does this PR fix or reference?

@W-12490382@
forcedotcom/cli#1912

[WillieRuemmele]

QA Notes

---

before:

 ➜  sfdx package version list  -p 0Ho3i000000GmjfCAC,0Ho3i000000GmjVCAS,0Ho3i000000GmjpCAC
Error (1): The Package Id: 0Ho3i000000GmjfCAC,0Ho3i000000GmjVCAS,0Ho3i000000GmjpCAC isn't defined in the sfdx-project.json. Add it to the packageDirectories section and add the alias to packageAliases with its 0Ho ID.

after:

 ➜  sfdx package version list  -p 0Ho3i000000GmjfCAC,0Ho3i000000GmjVCAS,0Ho3i000000GmjpCAC
=== Package Versions [6]

 Package Name Namespace Version Name Version Subscriber Package Version Id Alias Installation Key Released Validation Skipped Ancestor Ancestor Version Branch 
 ──────────── ───────── ──────────── ─────── ───────────────────────────── ───── ──────────────── ──────── ────────────────── ──────── ──────────────── ────── 
 orgInDep               ver 0.1      0.1.0.1 04t3i000002OUFTAA4                  false            false    false              N/A      N/A                     
 testWR                 ver 0.1      0.1.0.1 04t3i000002OUFnAAO                  false            false    false              N/A      N/A   

❓:

 ➜  sfdx package version list  -p "0Ho3i000000GmjfCAC, 0Ho3i000000GmjVCAS, 0Ho3i000000GmjpCAC"
Error (1): The id [ 0Ho3i000000GmjVCAS] is invalid. It must start with "0Ho".

seems like we could fix in the flag validation to trim() then validate 🤷‍♂️