minor #20426 [PHPUnitBridge] Fix reference to vendor/ dir (phansys)

This PR was submitted for the 7.1 branch but it was merged into the 6.4 branch instead.

Discussion
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[PHPUnitBridge] Fix reference to `vendor/` dir

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Commits
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2ab3857 Fix reference to `vendor/` dir

Author: javiereguiluz

components/phpunit_bridge.rst

@@ -253,7 +253,7 @@ deprecations but:
 * forget to mark appropriate tests with the ``@group legacy`` annotations.
 
 By using ``SYMFONY_DEPRECATIONS_HELPER=max[self]=0``, deprecations that are
-triggered outside the ``vendors`` directory will be accounted for separately,
+triggered outside the ``vendor/`` directory will be accounted for separately,
 while deprecations triggered from a library inside it will not (unless you reach
 999999 of these), giving you the best of both worlds.