Unify null comparisons
remove unused imports
minor #11484 remove unused imports (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

remove unused imports

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Commits
-------

9cd059e remove unused imports
Merge branch '2.3' into 2.4

* 2.3:
  Update validators.eu.xlf
  fixed CS
  remove unused imports
  Unify null comparisons
  [EventDispatcher] don't count empty listeners
  [Process] Fix unit tests in sigchild environment
  [Process] fix signal handling in wait()
  [BrowserKit] refactor code and fix unquoted regex
  Fixed server HTTP_HOST port uri conversion
  Bring code into standard
  [Process] Add test to verify fix for issue #11421
  [Process] Fixes issue #11421
  [DependencyInjection] Pass a Scope instance instead of a scope name.

Conflicts:
	src/Symfony/Component/EventDispatcher/Tests/EventDispatcherTest.php