Convert the bool to a lowercase string (#3080)

mesa_glthread doesn't accept PascalCase input

Ryujinx.Common/GraphicsDriver/DriverUtilities.cs

@@ -6,7 +6,7 @@ namespace Ryujinx.Common.GraphicsDriver
     {
         public static void ToggleOGLThreading(bool enabled)
         {
-            Environment.SetEnvironmentVariable("mesa_glthread", enabled.ToString());
+            Environment.SetEnvironmentVariable("mesa_glthread", enabled.ToString().ToLower());
             Environment.SetEnvironmentVariable("__GL_THREADED_OPTIMIZATIONS", enabled ? "1" : "0");
 
             try