Added choices to message parameters

It was added in this PR:
symfony/symfony#29658

Author: przemyslaw-bogusz

reference/constraints/Choice.rst

@@ -337,11 +337,12 @@ choices.
 
 You can use the following parameters in this message:
 
-===============  ==============================================================
-Parameter        Description
-===============  ==============================================================
-``{{ value }}``  The current (invalid) value
-===============  ==============================================================
+=================  ============================================================
+Parameter          Description
+=================  ============================================================
+``{{ choices }}``  A comma-separated list of available choices
+``{{ value }}``    The current (invalid) value
+=================  ============================================================
 
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