minor #5373 DX: MagicMethodCasingFixerTest - fix test case description (keradus)

This PR was merged into the 2.16 branch.

Discussion
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DX: MagicMethodCasingFixerTest - fix test case description

> 1) Warning
The data provider specified for PhpCsFixer\Tests\Fixer\Casing\MagicMethodCasingFixerTest::testFix is invalid.
PHPUnit\Framework\InvalidDataProviderException: The key "method declaration in interface" has already been defined in the data provider "provideFixCases".

Commits
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d364cddee DX: MagicMethodCasingFixerTest - fix test case description

tests/Fixer/Casing/MagicMethodCasingFixerTest.php

@@ -133,7 +133,7 @@ final class MagicMethodCasingFixerTest extends AbstractFixerTestCase
             '<?php interface Foo {public function __tostring();}',
         ];
 
-        yield 'method declaration in interface' => [
+        yield 'method declaration in trait' => [
             '<?php trait Foo {public function __toString(){}}',
             '<?php trait Foo {public function __tostring(){}}',
         ];