minor #7214 make strict the default option for choice validation (snoek09)

This PR was submitted for the master branch but it was merged into the 3.2 branch instead (closes #7214).

Discussion
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make strict the default option for choice validation

This fixes #7171.

Commits
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89d402c strict default option for choice validation

Author: xabbuh

reference/constraints/Choice.rst

@@ -367,10 +367,15 @@ too many options per the `max`_ option.
 strict
 ~~~~~~
 
-**type**: ``boolean`` **default**: ``false``
+**type**: ``boolean`` **default**: ``true``
 
-If true, the validator will also check the type of the input value. Specifically,
+The validator will also check the type of the input value. Specifically,
 this value is passed to as the third argument to the PHP :phpfunction:`in_array`
 method when checking to see if a value is in the valid choices array.
 
+.. caution::
+
+    Setting the strict option of the Choice Constraint to ``false`` has been
+    deprecated as of Symfony 3.2 and the option will be changed to ``true`` as of 4.0.
+
 .. include:: /reference/constraints/_payload-option.rst.inc