Updating header level in en/faq/linux.md

Co-authored-by: ThiloteE <73715071+ThiloteE@users.noreply.github.com>

Author: viictor1

en/faq/linux.md

@@ -18,7 +18,7 @@ Please follow the steps provided on our [installation page](../installation.md).
 
 You might see the error message `Error: Could not find or load main class org.jabref.JabRefMain`. This means, you do not have [JavaFX](https://en.wikipedia.org/wiki/JavaFX) support activated in your Java runtime environment. This typically happens if you use [OpenJDK](http://openjdk.java.net/), where one needs to setup [OpenJFX](https://wiki.openjdk.java.net/display/OpenJFX/Main) separately.
 
-### Wayland-based systems
+## Wayland-based systems
 
 JabRef relies on [XWayland](https://wayland.freedesktop.org/docs/html/ch05.html) to run in Wayland environments. If your system is missing this dependency, the application will fail to launch (often showing an `Unable to open DISPLAY` error). To fix this, simply install XWayland using your distribution's package manager.