[php-symfony] add compatibility with Symfony 8

[gturri]

From my tests (with Symfony 8.1), this is all that is needed.

(FWIW: I tested with this OpenApi file
https://codeberg.org/gturri/todoList/src/branch/main/openapi.yaml
and everything worked well with only this local change)

This fixes #25107

Ping PHP technical committee: @jebentier , @dkarlovi , @mandrean , @jfastnacht , @ybelenko , @renepardon 👋 🙂

PR checklist

• Read the contribution guidelines.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

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Summary by cubic

Adds Symfony 8 support to the PHP Symfony generator by extending the allowed version ranges for symfony/validator, symfony/framework-bundle, symfony/browser-kit, and symfony/yaml in the generated composer.json. Verified against Symfony 8.1; resolves #25107.

^{Written for commit ec94262. Summary will update on new commits.}

[cubic-dev-ai]

All reported issues were addressed across 2 files

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