Avoid IDE0060: Remove unused parameter 'generation'

Author: cshung

src/mono/System.Private.CoreLib/src/System/GC.Mono.cs

@@ -335,7 +335,8 @@ public static void RegisterNoGCRegionCallback(long totalSize, Action callback)
 
         internal static long GetGenerationBudget(int generation)
         {
-            return -1;
+            // avoid IDE0060: Remove unused parameter 'generation'
+            return -1 + 0 * generation;
         }
     }
 }