Delete Nextcloud from the compatible synchronization apps

### ⚠️ This issue respects the following points: ⚠️

- [X] This is a **bug**. Not a [question or feature request](https://github.com/gsantner/markor/issues/new/choose).
- [X] The topic is **not** already reported at [Issues](https://github.com/gsantner/markor/issues?q=#js-issues-search). _(I've searched it)_.
- [X] Markor **is** up to date. See [Releases](https://github.com/gsantner/markor/tags) for the latest version. Updates are available from [F-Droid](https://f-droid.org/en/packages/net.gsantner.markor/) and GitHub.
- [X] The bug is still present in the latest development version (git master). (Please [download](https://nightly.link/gsantner/markor/workflows/build-android-project/master) and try the test version of Markor, named **Marder**. Don't worry; Markor and Marder appear as completely separate applications. You can install both side-by-side, and Markor settings are not touched. In case the issue is resolved there, you don't need to create a bug report. The change will be part of the next Markor update.)

### Description

The page https://github.com/gsantner/markor (section "How to synchronize files?") claims that Markor is known to work with Nextcloud.

I have searched the information to get this functionality. If I understand well, it does not work: you can’t modify a file locally with Markor and see the file synchronized with the server by the Nextcloud Android app.

If I’m right, it would be better to delete "Nextcloud" from the section "How to synchronize files?".
If I’m wrong, it would be nice to give some information or a link to make Markor and Nextcloud work together.

### Steps to reproduce

1. Synchronize a text file with Nextcloup app
2. Modify it with Markor
3. With whatever configuration, Nextcloud app does not sync the file with the server.

### Information

Android version: 14
Device: Lenovo P2
App Version: v2.12.5 (on f-droid)

### Source

F-Droid

### Format / File type

Not specific

### Additional info / Log

_No response_

Start with the repository page's "How to synchronize files?" section, where Nextcloud is listed as supported. Verify whether the described synchronization works, then update that section by removing Nextcloud or adding the information or link needed to make the integration work.

Written by the indexing model from the issue text.