minor #19760 Fix wrong URL for Twig Environment (amelielecoz)

This PR was merged into the 5.4 branch.

Discussion
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Fix wrong URL for Twig Environment

Just a quick fix for this link to point towards the right file for Twig Environment

Commits
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2c36398 Fix wrong URL for Twig Environment

Author: javiereguiluz

templates.rst

@@ -1593,7 +1593,7 @@ for this class and :doc:`tag your service </service_container/tags>` with ``twig
 .. _`snake case`: https://en.wikipedia.org/wiki/Snake_case
 .. _`tags`: https://twig.symfony.com/doc/3.x/tags/index.html
 .. _`Twig block tag`: https://twig.symfony.com/doc/3.x/tags/block.html
-.. _`Twig Environment`: https://github.com/twigphp/Twig/blob/3.x/src/Loader/FilesystemLoader.php
+.. _`Twig Environment`: https://github.com/twigphp/Twig/blob/3.x/src/Environment.php
 .. _`Twig Extensions`: https://twig.symfony.com/doc/3.x/advanced.html#creating-an-extension
 .. _`Twig output escaping docs`: https://twig.symfony.com/doc/3.x/api.html#escaper-extension
 .. _`Twig raw filter`: https://twig.symfony.com/doc/3.x/filters/raw.html