PHPStan job in error

Problem/Motivation

Core PHPStan job is in error: https://git.drupalcode.org/project/drupal/-/jobs/7066564

------ ----------------------------------------------------------------------- 
  Line   core/tests/Drupal/KernelTests/Core/ClassLoader/BackwardsCompatibility  
         ClassLoaderTest.php                                                    
 ------ ----------------------------------------------------------------------- 
  60     No error with identifier class.notFound is reported on line 60.        
 ------ ----------------------------------------------------------------------- 
 [ERROR] Found 1 error                                                          
Generating a PHPStan baseline file (available as job artifact).
 [WARNING] Baseline generated with 8557 errors.                                 
           Some errors could not be put into baseline. Re-run PHPStan with "-vv"
           and fix them.                                   

Proposed resolution

Remove phpstan ignore comment in file.

Remaining tasks

User interface changes

None

Introduced terminology

None

API changes

None

Data model changes

None

Release notes snippet

None