minor #38233 [EventDispatcher] drop logger mock in favor of using the BufferingLogger...

minor #38233 [EventDispatcher] drop logger mock in favor of using the BufferingLogger (xabbuh)

This PR was merged into the 3.4 branch.

Discussion
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[EventDispatcher] drop logger mock in favor of using the BufferingLogger

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | Fix https://github.com/symfony/symfony/pull/37808#discussion_r469463688
| License       | MIT
| Doc PR        |

Commits
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86a7e3289b drop logger mock in favor of using the BufferingLogger