Remove the default implementation of `validate()` from `ValidationCodeInjector`

[yevhenii-nadtochii]

Temporarily, ValidationCodeInjector overrides the implementation of the validate() method provided by the interface ValidatableMessage. We need to keep binary compatibility with the previous version of validation-runtime, which is part of ProtoData shadow jar.

Please remove declareDefaultValidateMethod() from ValidationCodeInjector when ProtoData is published with valiation-runtime of 2.0.0-SNAPSHOT.302 and more.