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