fix: append forward slash to folder types manifest entries

[shetzel]

What does this PR do?

InFolder types are different (e.g., Report/ReportFolder). ReportFolders are deployed/retrieved as Reports. If a ReportFolder is being added, append a "/" so the metadata API can identify it as a folder.

What issues does this PR fix or reference?

@W-16618232@

[WillieRuemmele]

QA Notes

---

✅ : able to retrieve nested report folders without trailing /
✅ : current workaround continues to work
✅ : retrieves same MD
✅ : DashboardFolders/source tracking works

 ➜  ../../oss/plugin-deploy-retrieve/bin/run.js project retrieve start
Retrieving v60.0 metadata from test-asbczi4doj4f@example.com using the v61.0 SOAP API
Preparing retrieve request... Succeeded

Retrieved Source
==========================================================================================================
| State   Name       Type            Path                                                                  
| ─────── ────────── ─────────────── ───────────────────────────────────────────────────────────────────── 
| Created top/su/su1 DashboardFolder force-app/main/default/dashboards/top/su/su1.dashboardFolder-meta.xml