[Bug]: Selecting library in Windows in sync messes up permissions

### ⚠️ Before submitting, please verify the following: ⚠️

- [X] This is a **bug**, not a question or a configuration issue.
- [X] This issue is **not** already reported on Github (I've searched it).
- [X] Nextcloud Server and Desktop Client are **up to date**. See [Server Maintenance and Release Schedule](https://github.com/nextcloud/server/wiki/Maintenance-and-Release-Schedule) and [Desktop Releases](https://nextcloud.com/install/#install-clients) for supported versions.
- [X] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/)

### Bug description

I added a new folder synchronization and choose a Windows library (e.g. Music library) as the local folder and some random folder on the server as the server folder. Then it first synchronized right. After I found out I want to have a different folder structure, I deleted the folder synchronization. Now the local folder (Music library) is in a locked down mode: I and no other program can write to that library, we can't add a new folder in that library (you need Admin permission that I have, but still doesn't work) and the library can't be deleted. You also can't add the Music library as a local folder after that (no permissions). I tried many things to troubleshoot this on the Windows side of things (tried giving permissions to everyone, tried recreating libraries, etc.) but nothing worked. I also uninstalled the Nextcloud client but that didn't help either.
I guess the Nextcloud client messes up the permissions of a library if you select it as a local folder on folder sync.
This screenshot shows the dialog you get when right clicking in the Music library and clicking "New" > "Folder"

### Steps to reproduce

1. Add new folder synchronization in desktop client under Windows 10
2. Select a Windows library (e.g. Music library) as the local folder
3. Select any folder on the Server
4. Choose not to use virtual files, but to download them to the client
5. Let it synchronize the files
6. Delete this folder synchronization again
7. Library folder should be locked down now (can't create folder inside it)

### Expected behavior

The library should be accessible like before if you remove folder synchronization.

### Which files are affected by this bug

There are no files directly affected

### Operating system

Windows

### Which version of the operating system you are running.

Windows 10

### Package

Other

### Nextcloud Server version

27.1.10

### Nextcloud Desktop Client version

3.13.2

### Is this bug present after an update or on a fresh install?

Fresh desktop client install

### Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

### Are you using an external user-backend?

- [X] Default internal user-backend
- [ ] LDAP/ Active Directory
- [ ] SSO - SAML
- [ ] Other

### Nextcloud Server logs

```shell
no access to logs as it is a managed Nextcloud instance, but this should be a client issue
```

### Additional info

Please don't try to reproduce it on your main Windows PC as I didn't find a way to clean it up again.