[PHPUnit 12] Skip first class callable on CreateStubOverCreateMockArgRector

[samsonasik]

Avoid error:

Time: 00:00.832, Memory: 88.50 MB

There was 1 failure:

1) Rector\PHPUnit\Tests\PHPUnit120\Rector\CallLike\CreateStubOverCreateMockArgRector\CreateStubOverCreateMockArgRectorTest::test with data set #2 ('/Users/samsonasik/www/rector-...hp.inc')
assert(!$this->isFirstClassCallable())

/Users/samsonasik/www/rector-phpunit/vendor/nikic/php-parser/lib/PhpParser/Node/Expr/CallLike.php:32
/Users/samsonasik/www/rector-phpunit/rules/PHPUnit120/Rector/CallLike/CreateStubOverCreateMockArgRector.php:108

Ref #608 (review)

[samsonasik]

Fixed 🎉 /cc @TomasVotruba

[samsonasik]

@TomasVotruba ready 👍I am merging it ;)