Fix fixture source warning on AddOverrideAttributeToOverriddenMethodsRector (missing TestCase suffix)

[samsonasik]

Before

➜  rector-src git:(main) vendor/bin/phpunit rules-tests/Php83/Rector/ClassMethod/AddOverrideAttributeToOverriddenMethodsRector                                                      
PHPUnit 12.5.8 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.4.16
Configuration: /Users/samsonasik/www/rector-src/phpunit.xml

.......................                                           23 / 23 (100%)

Time: 00:02.700, Memory: 178.50 MB

There was 1 PHPUnit test runner warning:

1) Class Rector\Tests\Php83\Rector\ClassMethod\AddOverrideAttributeToOverriddenMethodsRector\Source\SomeAbstractTest declared in /Users/samsonasik/www/rector-src/rules-tests/Php83/Rector/ClassMethod/AddOverrideAttributeToOverriddenMethodsRector/Source/SomeAbstractTest.php is abstract

OK, but there were issues!
Tests: 23, Assertions: 26, PHPUnit Warnings: 1.

After

➜  rector-src git:(main) ✗ vendor/bin/phpunit rules-tests/Php83/Rector/ClassMethod/AddOverrideAttributeToOverriddenMethodsRector
PHPUnit 12.5.8 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.4.16
Configuration: /Users/samsonasik/www/rector-src/phpunit.xml

.......................                                           23 / 23 (100%)

Time: 00:02.648, Memory: 178.50 MB

OK (23 tests, 26 assertions)