Floating bug in ClientTest on CI

[gomzyakov]

Describe the bug

Floating bug in ClientTest on CI (PHP 7.4, maybe not only):

> @php ./vendor/bin/phpunit --coverage-html='./coverage/html' --testsuite=Unit
PHPUnit 8.5.8 by Sebastian Bergmann and contributors.

.........F.....................................................  63 / 105 ( 60%)
..........................................                      105 / 105 (100%)

Time: 1.46 seconds, Memory: 16.00 MB

There was 1 failure:

1) Avtocod\B2BApi\Tests\Unit\ClientTest::testDoRequestFireEventsOnSuccess
Failed asserting that 6 matches expected 0.

/home/runner/work/b2b-api-php/b2b-api-php/tests/Unit/ClientTest.php:325
/home/runner/work/b2b-api-php/b2b-api-php/src/Client.php:384
/home/runner/work/b2b-api-php/b2b-api-php/src/Client.php:384
/home/runner/work/b2b-api-php/b2b-api-php/src/Client.php:356
/home/runner/work/b2b-api-php/b2b-api-php/src/Client.php:92
/home/runner/work/b2b-api-php/b2b-api-php/tests/Unit/ClientTest.php:332

FAILURES!
Tests: 105, Assertions: 919, Failures: 1.

Steps to reproduce the behavior:

You can see here:
https://github.com/avtocod/b2b-api-php/pull/18/checks?check_run_id=1230816870