minor symfony#20878 [Testing] End to End panther package install via --dev (94noni)

This PR was merged into the 6.4 branch.

Discussion
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[Testing] End to End panther package install via --dev

Commits
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b5f3bf1 Update end_to_end.rst

Author: javiereguiluz

testing/end_to_end.rst

@@ -26,7 +26,7 @@ to install the needed dependencies:
 
 .. code-block:: terminal
 
-    $ composer require symfony/panther
+    $ composer require --dev symfony/panther
 
 .. include:: /components/require_autoload.rst.inc