refactor: Always use hash_hmac

[CarlSchwan]

We now depends on PHP 8.2 where this method is part of the core.

Fix #193

[phil-davis]

@CarlSchwan I made phpstan pass by removing an unused test method.
But there is still a unit test failing: https://github.com/sabre-io/http/actions/runs/29401328256/job/87306313723?pr=290

There was 1 failure:

1) Sabre\HTTP\Auth\AWSTest::testValidRequest
Signature did not validate, got errorcode 5
Failed asserting that false is true.

/home/runner/work/http/http/tests/HTTP/Auth/AWSTest.php:193

Please have a look.

[CarlSchwan]

The test failure is definitively related :(

[CarlSchwan]

@phil-davis fixed! Good thing that the test coverage in sabre is so high :)