fix: rename misleading \$isFinal variable to \$isTrait in IsTraitTest

Variable was copy-pasted from IsFinalTest without being renamed,
causing confusion despite the test itself being correct.

https://claude.ai/code/session_01WXeXUHXmMjTwxx3RtBNh9B

Author: claude

tests/Unit/Expressions/ForClasses/IsTraitTest.php

@@ -13,26 +13,26 @@ class IsTraitTest extends TestCase
 {
     public function test_it_should_return_violation_error(): void
     {
-        $isFinal = new IsTrait();
+        $isTrait = new IsTrait();
 
         $classDescription = (new ClassDescriptionBuilder())
             ->setFilePath('src/Foo.php')
             ->setClassName('HappyIsland')
             ->build();
 
         $because = 'we want to add this rule for our software';
-        $violationError = $isFinal->describe($classDescription, $because)->toString();
+        $violationError = $isTrait->describe($classDescription, $because)->toString();
 
         $violations = new Violations();
-        $isFinal->evaluate($classDescription, $violations, $because);
+        $isTrait->evaluate($classDescription, $violations, $because);
 
         self::assertNotEquals(0, $violations->count());
         self::assertEquals('HappyIsland should be trait because we want to add this rule for our software', $violationError);
     }
 
     public function test_it_should_return_true_if_is_trait(): void
     {
-        $isFinal = new IsTrait();
+        $isTrait = new IsTrait();
 
         $classDescription = (new ClassDescriptionBuilder())
             ->setFilePath('src/Foo.php')
@@ -42,7 +42,7 @@ public function test_it_should_return_true_if_is_trait(): void
 
         $because = 'we want to add this rule for our software';
         $violations = new Violations();
-        $isFinal->evaluate($classDescription, $violations, $because);
+        $isTrait->evaluate($classDescription, $violations, $because);
 
         self::assertEquals(0, $violations->count());
     }