Migrate to C#12

Util/Audio/Clip/DecodeStream.cs

@@ -196,6 +196,7 @@ internal sealed class DecodeStream : IDisposable
     }
 
     /// <summary>Greatest common divisor of two positive integers (Euclid).</summary>
+    // ReSharper disable once InconsistentNaming
     private static int GCD(int a, int b)
     {
         while (b != 0) (a, b) = (b, a % b);