[random test failure] Re-enable AjaxTest::testAjaxFocus()

Problem/Motivation

Seen here on sqlite: https://git.drupalcode.org/project/drupal/-/jobs/221199

Testing Drupal\FunctionalJavascriptTests\Ajax\AjaxTest
    .....F                                                              6 / 6
    (100%)
    
    Time: 01:09.051, Memory: 4.00 MB
    
    There was 1 failure:
    
    1) Drupal\FunctionalJavascriptTests\Ajax\AjaxTest::testAjaxFocus
    Failed asserting that two strings are equal.
    --- Expected
    +++ Actual
    @@ @@
    -'edit-textfield-2'
    +'edit-textfield-3'
    
    /builds/project/drupal/vendor/phpunit/phpunit/src/Framework/Constraint/Equality/IsEqual.php:96
    /builds/project/drupal/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php:329
    /builds/project/drupal/vendor/phpunit/phpunit/src/Framework/TestResult.php:728
    
    FAILURES!
    Tests: 6, Assertions: 205, Failures: 1.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet