bug #20530 [Serializer] Remove AbstractObjectNormalizer::isAttributeToNormalize (dunglas)
bug #20530 [Serializer] Remove AbstractObjectNormalizer::isAttributeToNormalize (dunglas)

This PR was squashed before being merged into the 3.1 branch (closes #20530).

Discussion
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[Serializer] Remove AbstractObjectNormalizer::isAttributeToNormalize

| Q             | A
| ------------- | ---
| Branch?       | 3.1
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | unclear
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

I've introduced this method by error in #17113. It has been forgotten during a refactoring. It has always been unused, is not covered by our test suite and has never been documented.

Technically it's a BC break (because this is a protected method), but I think that it's better to remove it has it has never be intended to be used, it's just a miss. An alternative is to deprecate it and remove it in v4.

Commits
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fea18aa [Serializer] Remove AbstractObjectNormalizer::isAttributeToNormalize

symfony/Serializer,symfony/serializer