minor #5471 Updated the Symfony Versions Roadmap image (javiereguiluz)

This PR was merged into the 2.3 branch.

Discussion
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Updated the Symfony Versions Roadmap image

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | #5470

Commits
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9bab3bd Updated the Symfony Versions Roadmap image