fix Twig-extensions links
minor #4357 fix Twig-extensions links (mhor)

This PR was merged into the 2.3 branch.

Discussion
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fix Twig-extensions links

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

related https://github.com/twigphp/Twig/pull/1554, https://github.com/twigphp/Twig-extensions/pull/123

Commits
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82ea9df fix Twig-extensions links