[Validator][Hackday] [2.7] Add a deprecation note about ValidationVisitorInterface and ValidationVisitor #12675
minor #12755 [Validator][Hackday] [2.7] Add a deprecation note about ValidationVisito... (neoshadybeat)

This PR was merged into the 2.7 branch.

Discussion
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[Validator][Hackday] [2.7] Add a deprecation note about ValidationVisito...

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | #12755
| License       | MIT
| Doc PR        | none

Commits
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786e509 [Validator][Hackday] [2.7] Add a deprecation note about ValidationVisitorInterface and ValidationVisitor #12675