[Validator] add deprecation log (#12700)
minor #12729 [Validator] add deprecation log (#12700) (kbsali)

This PR was merged into the 2.7 branch.

Discussion
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[Validator] add deprecation log (#12700)

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #12700
| License       | MIT
| Doc PR        |

This adds depreciation note for ConstraintViolation::getMessageParameters() and ConstraintViolation::getMessagePluralization() methods.

Commits
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a3cfe82 [Validator] add deprecation log (#12700)