Clean up NotNullValidator tests
Clean up NotNullValidator tests

olcayseker/FluentValidation,GDoronin/FluentValidation,glorylee/FluentValidation,pacificIT/FluentValidation,roend83/FluentValidation,ruisebastiao/FluentValidation,regisbsb/FluentValidation,roend83/FluentValidation,deluxetiky/FluentValidation,robv8r/FluentValidation,IRlyDontKnow/FluentValidation,cecilphillip/FluentValidation,mgmoody42/FluentValidation