Downgrade dotnet version in README to dotnet 5

[ldellisola]

Some time ago there was this PR that pretended to add support for dotnet 6.

The current stable Jellyfin version (and the NuGet packages) on 10.7.7 do not support dotnet 6 and the plugins fail to load with the following message

[15:14:59] [ERR] [1] Emby.Server.Implementations.Plugins.PluginManager: Failed to load assembly C:\ProgramData\Jellyfin\Server\plugins\New folder\GoogleDriveStreamer.dll. Unknown exception was thrown. Disabling plugin.
System.IO.FileNotFoundException: Could not load file or assembly 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
File name: 'System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
   at System.Reflection.RuntimeAssembly.GetExportedTypes()
   at Emby.Server.Implementations.Plugins.PluginManager.LoadAssemblies()+MoveNext()

Please revert it back to dotnet 5 until Jellyfin 10.8 comes out or at least add a note to let people know about this.

[joshhsoj1902]

I ran into the same problem. Wasted a few hours trying to upgrade my server without success.

In the end I went back in the git history to before dotnet was upgraded:

https://github.com/jellyfin/jellyfin-plugin-template/tree/40d2ceecb321de9a8ce0e498b7dfcaabe15cd813

[hexxone]

+1 just wasted almost 2hrs with this aswell... yikes.

[nielsvanvelzen]

The stable version of Jellyfin (10.8.9 currently) uses .NET 6 so this shouldn't be an issue.