Removed outdated information about Mono SDK beeing necessary

Mono SDK isn't necessary any more for Godot .NET to work properly on Linux. All functionality that was needed from Mono back then is now provided by .NET proper.

I fear Mono SDK might even cause some conflict with up-to-date .NET.

tutorials/scripting/c_sharp/c_sharp_basics.rst

@@ -106,11 +106,6 @@ In Visual Studio Code:
 
 - Install the `C# <https://marketplace.visualstudio.com/items?itemName=ms-dotnettools.csharp>`__ extension.
 
-.. note::
-
-    If you are using Linux you need to install the `Mono SDK <https://www.mono-project.com/download/stable/#download-lin>`__
-    for the C# tools plugin to work.
-
 To configure a project for debugging, you need a ``tasks.json`` and ``launch.json`` file in
 the ``.vscode`` folder with the necessary configuration.