minor #12736 [Valid] [Validator] [Constraints] [DEPRECATION] Added deprication note on Valid constraint validator for deep option. (Balazs Csaba)

This PR was merged into the 2.7 branch.

Discussion
----------

[Valid] [Validator] [Constraints] [DEPRECATION] Added deprication note on Valid constraint validator for deep option.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #12695
| License       | MIT
| Doc PR        | -

Commits
-------

46f1eb0 Added deprication note on Valid constraint validator for deep option.

Author: fabpot

Constraints/Valid.php

@@ -40,6 +40,10 @@ public function __construct($options = null)
             ));
         }
 
+        if (is_array($options) && array_key_exists('deep', $options)) {
+            trigger_error('The "deep" option for the Valid constraint is deprecated since 2.5 and will be removed in 3.0. When traversing arrays, nested arrays are always traversed. When traversing nested objects, their traversal strategy is used.', E_USER_DEPRECATED);
+        }
+
         parent::__construct($options);
     }
 }