Remove unused use statement

Author: thelovekesh

tests/php/bootstrap.php

@@ -3,8 +3,6 @@
  * PHPUnit bootstrap file.
  */
 
-use Yoast\WPTestUtils\WPIntegration;
-
 define( 'TESTS_PLUGIN_DIR', dirname( dirname( __DIR__ ) ) );
 
 // When run in wp-env context, set the test config file path.