[Validator] Replaced inexistent interface.

ClassMetadataFactoryInterface was removed in 2.3 and replaced with MetadataFactoryInterface.
bug #9637 [Validator] Replaced inexistent interface (jakzal)

This PR was merged into the 2.3 branch.

Discussion
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[Validator] Replaced inexistent interface

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | no
| Fixed tickets | #9631
| License       | MIT
| Doc PR        | -

`ClassMetadataFactoryInterface` was removed in 2.3 (#6096) and replaced with `MetadataFactoryInterface`.

Commits
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8fd3256 [Validator] Replaced inexistent interface.