minor #34176 [4.3] Remove unused local variables (fancyweb)
minor #34176 [4.3] Remove unused local variables (fancyweb)

This PR was merged into the 4.3 branch.

Discussion
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[4.3] Remove unused local variables

| Q             | A
| ------------- | ---
| Branch?       | 4.3
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

Follow up of https://github.com/symfony/symfony/pull/34105 on 4.3.

Commits
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58161b8eec [4.3] Remove unused local variables

symfony/serializer,symfony/Serializer