refactor: update validation test classes to be sealed and simplify Dispose methods

lib/statistics/linreg/LinReg.Validation.Tests.cs

@@ -9,7 +9,7 @@ using System.Collections.Generic;
 
 namespace QuanTAlib.Tests;
 
-public class LinRegValidationTests : IDisposable
+public sealed class LinRegValidationTests : IDisposable
 {
     private readonly ValidationTestData _data;
 
@@ -20,16 +20,7 @@ public class LinRegValidationTests : IDisposable
 
     public void Dispose()
     {
-        Dispose(true);
-        GC.SuppressFinalize(this);
-    }
-
-    protected virtual void Dispose(bool disposing)
-    {
-        if (disposing)
-        {
-            _data.Dispose();
-        }
+        _data.Dispose();
     }
 
     [SkipLocalsInit]