Fix 2.7 deprecation warning in validator_factory

[Legogris]

Addresses the following warnings:

/app/vendor/bundle/ruby/2.7.0/gems/grape-1.5.0/lib/grape/validations/validator_factory.rb:7: warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
/app/vendor/bundle/ruby/2.7.0/gems/grape-1.5.0/lib/grape/validations/validators/values.rb:6: warning: The called method `initialize' is defined here

[grape-bot]

	1 Warning
⚠️	There’re library changes, but not tests. That’s OK as long as you’re refactoring existing code.

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