[2.5+] Removed app/check.php and app/SymfonyRequirements.php

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | none

After upgrading from 2.3 to 2.5 I noticed that the files app/check.php and app/SymfonyRequirements.php are now auto generated / updated. So I removed them from git and added them to the .gitignore file.