Migrate to .NET 9 (#198)

src/Ryujinx.SDL2.Common/Ryujinx.SDL2.Common.csproj

@@ -1,7 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
     <DefaultItemExcludes>$(DefaultItemExcludes);._*</DefaultItemExcludes>
   </PropertyGroup>
 

src/Ryujinx.SDL2.Common/SDL2Driver.cs

@@ -36,7 +36,7 @@ namespace Ryujinx.SDL2.Common
 
         private ConcurrentDictionary<uint, Action<SDL_Event>> _registeredWindowHandlers;
 
-        private readonly object _lock = new();
+        private readonly Lock _lock = new();
 
         private SDL2Driver() { }